PITTSBURGH — County detectives have gotten a search warrant for the records of cellphones belonging to two family members of a boy charged with stabbing 20 students and a security guard at his western Pennsylvania high school.

Westmoreland County detectives have been trying to determine whether Alex Hribal, 16, of Murrysville used the phones to threaten any of the students he stabbed April 9 at Franklin Regional High School, about 15 miles east of Pittsburgh.

Hribal’s attorney Patrick Thomassey doesn’t dispute his role in the stabbings, which Thomassey acknowledges were carried out with two large kitchen knives Hribal took from his home that morning. Thomassey has suggested the boy may have been bullied, though police have said they haven’t found any evidence to support that.

Investigators previously obtained a warrant for Hribal’s cellphone records, but got another one Monday for phones belonging to two family members whom authorities are not naming.

“They’ve had a couple of those phones for quite a long time,” Thomassey said Tuesday. “I don’t know what’s taken so long to search for the records.”

The defense attorney said he’s more concerned about Hribal’s mental state, which is why he petitioned the court last week to move Hribal from a juvenile detention center to a secure mental health facility. No hearing has been scheduled on that request.

Hribal faces formal arraignment July 23 on 21 counts each of attempted homicide and aggravated assault, plus a school weapons violation.

Thomassey has said he’ll ask a judge to move the case to juvenile court, where Hribal can be incarcerated or supervised only until he’s 21, instead of Common Pleas court, where Hribal faces prison if convicted.