A high school student accused of killing a classmate and the classmate's parents in the middle of the night was taken to a mental institution 3 1/2 weeks after the killings because he threatened suicide, authorities said in court papers filed Tuesday.

The teenager's father also gave investigators a knife that his son said he used in the May 12 killings and told police where to find the shoes the boy was wearing the night of the murders, authorities said in a search warrant application. The tread pattern on the shoes appears to match bloody shoe prints left at the scene, investigators said.

Alec Devon Kreider, 16, of Lancaster, was arrested at a mental institution over the weekend after his father, Timothy Kreider, said that the teenager had confessed to the killings. Kreider had told detectives the day after the murders that he and 16-year-old victim Kevin T. Haines were best friends.

The court papers filed Tuesday seek permission to take hair, fingerprints and blood samples from Kreider, to photograph him and record his height and weight. The warrant was executed before noon.

In the papers, authorities said Kreider was taken into custody June 5 for an involuntary commitment after threatening to shoot himself with a handgun at the home of his mother, Angela Kreider. Angela and Timothy Kreider are separated and share custody of Kreider, according to the search warrant. Both their homes are within walking distance of the murder scene.

Kreider's attorney, John A. Kenneff, declined to comment.

The bodies of Thomas Alan Haines, 50, Lisa Ann Haines, 47, and their son were found at their house in a leafy neighborhood in Manheim Township after 2 a.m., a crime that investigators said had them stumped for several weeks.

Bloody footprints were found on the carpeted stairs and on a linoleum floor in a bathroom, and blood was recovered from a rear sliding-glass door that investigators said was left about 6 inches open, according to another search warrant that was unsealed Tuesday.

The Haineses' college-age daughter, Maggie, told investigators she was awakened by the screams of a male voice she believed was her brother. She said she "smelled blood" and ran to her parents room, where her mother told her to get help, according to the latest search warrant. She went to the home of a neighbor, who called 911.

Authorities have described Kevin Haines as the intended target, but declined to comment on a possible motive. They have said Kreider went to the home intending to smother Kevin, but instead stabbed him in the neck and chest. Thomas Haines was stabbed in the chest and his wife in the abdomen.

Kreider, who attends Manheim Township High School, was charged as an adult with three counts of murder. He was being held without bail. Authorities said they believe he acted alone.

Kreider allegedly confessed to his father on June 12. The father went to police Thursday.

A preliminary hearing in the case that had been scheduled for Wednesday has been indefinitely postponed, court officials said.