OPINION
¶ 1 Abraham David Sepahi was convicted of two counts of aggravated assault for shooting a fourteen-year-old victim in the stomach. The superior court held that the crimes for which Sepahi was convicted were dangerous crimes against a child and therefore sentenced Sepahi under the special sentencing provisions of Arizona Revised Statutes (“A.R.S.”) § 13-604.01(K) (Supp.1999). The court of appeals vacated those sentences, holding that Sepahi had not committed a dangerous crime against a child because there was no evidence that he was “peculiarly dangerous to children” or that he “pose[s] a direct and continuing threat to the children of Arizona.”
State v. Sepahi,
¶ 2 We granted review because the quantum of proof to establish that a crime is a “dangerous crime against children” under A.R.S. § 13-604.01 is an issue of statewide importance. We have jurisdiction pursuant to Article 6, Section 5(3) of the Arizona Constitution, and A.R.S. §§ 13-4031 and -4032(3) (2001). Because this case involves interpretation of a statute, our review is de novo.
State v. Christian,
I.
¶ 3 In September of 1999, Abraham Sepahi and a friend approached a young girl and an adult, both of whom were on the front porch of the adult’s trailer. Sepahi’s friend conversed with the adult about gang affiliations, and eventually the girl, afraid that the sitúa *322 tion could escalate into a fight, asked Sepahi and his friend to leave. When they did not, she became agitated and threatened to fight them both. Sepahi hit her on the arm, and she responded by hitting him on the head. Sepahi then pulled out a gun and fired one shot, hitting the girl in the stomach.
¶ 4 Sepahi was fourteen at the time of the incident, as was the victim. He was tried as an adult and convicted of aggravated assault causing serious physical injury, A.R.S. § 13-1204(A)(1) (Supp.1999), and aggravated assault involving the use of a deadly weapon or dangerous instrument, A.R.S. § 13-1204(A)(2). 1
¶ 5 The jury also found that, at the time of the incident, the victim was under the age of fifteen. At sentencing, the trial judge held that the offenses were dangerous crimes committed against a child as defined in A.R.S. § 13-604.01(L)(1)(b), and sentenced Sepahi pursuant to A.R.S. § 13-604.01(K) to two consecutive ten-year terms of imprisonment.
¶ 6 The court of appeals vacated the sentences, holding that the dangerous crimes against children statute did not apply to this case.
Sepahi,
II.
¶ 7 Section 13-604.01 requires enhanced penalties for persons convicted of a “dangerous crime against children.” The statute defines such a crime as one of fifteen enumerated offenses “that is committed against a minor who is under fifteen years of age.” A.R.S. § 13-604.01(L)(1). Aggravated assault resulting in serious injury or involving the discharge or use of a weapon is among the offenses listed. Id. Sepahi was convicted of two of the enumerated crimes, and it is undisputed that his victim was under the age of fifteen.
¶ 8 As the court of appeals correctly recognized, however, this does not end the inquiry under A.R.S. § 13-604.01. We held in
Williams
that even when a defendant is convicted of one of the statutorily enumerated crimes and the victim is younger than fifteen, “something more” is required to activate the special sentencing provisions of the statute.
A.
¶ 9
Williams
involved a defendant who, while driving drunk, crashed his truck into the back of a station wagon.
Williams,
¶ 10 The issue before this court in
Williams
was whether an offense enumerated in A.R.S. § 13-604.01(L)
2
was a “danger
*323
ous crime against children” whenever the victim was under the age of fifteen. We began, as we must in any ease involving statutory interpretation, with the language of the statute involved. Section 13-604.01(L) defines a “dangerous crime against children” as one “committed
against
a minor under fifteen years of age.” (Emphasis added.) Noting that the legislature had not chosen to define a dangerous crime simply as one in which the “victim is under fifteen years of age,” a phrase it had employed in other criminal statutes, we then set out to determine what the term “against a minor” meant.
Williams,
¶ 11 We found support for that conclusion in the legislative history of § 13-604.01, which was “calculated to reach criminals who specifically prey upon children” and “predators who pose a direct and continuing threat to the children of Arizona.”
Id.
Because the special penalties in the statute were intended to punish and deter such persons, we concluded that the legislature did not intend to apply § 13-604.01 to persons like Williams, who “fortuitously injure children by their unfocused conduct.”
Id.
at 103,
¶ 12 We therefore held in
Williams
that “[bjecause a ‘dangerous crime against children’ is defined as one ‘committed against a minor under fifteen years of age,’
the defendant’s conduct must be focused on, directed against, aimed at, or target a victim, under the age of fifteen.” Id.
(emphasis added). We stressed that the defendant need not know the victim’s age to be subject to sentencing under § 13-604.01, but rather held “only that the victim must be the person against whom the crime is directed.”
Id.
Because Williams’ criminal behavior was not “directed at or focused upon” a victim under the age of fifteen, we held that the enhanced sentencing provisions of § 13-604.01 did not apply.
Id.
at 104,
B.
¶ 13 In this case, as the court of appeals acknowledged, there was no doubt that Sepahi’s criminal conduct was “ ‘focused on, directed against, aimed at, or target[ed] a victim under the age of fifteen.’ ”
Sepahi,
¶ 14 We noted in
Williams
that while “the most natural reading of the definition of a ‘dangerous crime against children’ indicates that it refers to crimes that target or focus upon children, it can certainly be argued that the language is not so plain that it admits of no other interpretation.”
Williams,
¶ 15 In other words, when choosing between two possible interpretations of the words of the statute, we placed some empha
*324
sis on the concern of legislative proponents of the statute in determining that the “most natural” reading of § 13-604.01 was in fact appropriate. But it is a far step from that conclusion to the one reached below — that is, that the statute not only requires that the crime be “against” a child in the sense that the child is the target of the crime, but also that the perpetrator be shown to be “peculiarly dangerous” to children or “pose a direct and continuing threat to children.” Such an interpretation in effect amends the statute to require proof of elements not set forth by the legislature, and thus contravenes the “universal rule that courts will not enlarge, stretch, or expand a statute to matters not falling within its express provisions.”
State ex rel. Morrison v. Anway,
¶ 16 In the end, a statute’s language is the most reliable index of its meaning.
State v. Thompson,
¶ 17 Moreover, it is difficult to reconcile the notion that § 13-604.01 requires that the defendant pose “a direct and continuing threat to children” with the clear statement in
Williams
that the defendant need not know the age of the victim.
Williams,
¶ 18 Nor is a different conclusion compelled by our observation in
Williams
that “a dangerous crime against a child is a crime against a child
qua
child.”
Williams,
¶ 19 We therefore reaffirm the holding in
Williams
that in order to prove that a defendant has committed a dangerous crime against a child, the State must prove that the defendant committed one of the statutorily enumerated crimes and that his conduct was “focused on, directed against, aimed at, or targeted] a victim under the age of fifteen.”
Williams,
*325-329 hi.
¶ 20 Our conclusion that Sepahi’s offenses qualified as dangerous crimes against children under § 13-604.01 requires us to address briefly one other issue decided by the court of appeals. Sepahi argued below that the double punishment prohibition in A.R.S. § 13-116 (Supp.1999) precluded the imposition of consecutive sentences. The court of appeals concluded that the two counts of aggravated assault for which Sepahi was convicted constituted a single act for purposes of sentencing, and that § 13-116 therefore prohibited consecutive sentencing.
Sepahi
¶21 The State did not argue below that the aggravated assault counts were separate acts for purposes of application of § 13-116.
Id.
at 190 n. 2,
IV.
¶ 22 For the reasons above, we vacate the opinion of the court of appeals and remand this case to the court of appeals for further proceedings consistent with this opinion.
Notes
. Sepahi was also charged with attempted second degree murder, but was acquitted of that charge.
. Formerly A.R.S. § 13-604.01(K) (Supp.1986). Section 13-604.01 has been amended several times since Williams was decided. See 1993 Ariz. Sess. Laws, ch. 255, § 8; 1997 Ariz. Sess. Laws, ch. 179, § 1; 1998 Ariz. Sess. Laws, ch. 281, § 1. For ease of reference, we cite to the version now in effect, which does not differ in any material respect from the statute interpreted in Williams.
. Sepahi argued for the first time in his supplemental brief in this court that § 13-604.01 runs afoul of the rule announced in
Apprendi v. New Jersey,
In any event, in light of our holding today that § 13-604.01 requires only that the defendant’s conduct be focused on, directed against, aimed at, or targeted at a victim under the age of fifteen, any
Apprendi
error would be harmless.
See United States v. Cotton,
. As the court of appeals noted,
State v. Arnoldi,
