Police said they still have not established a motive for the murder of university student Matthew Weaver, who was found shot to death along with his brother and parents in their Pennsylvania home last Thursday.

Police concluded, however, the killing was a murder-suicide by the rising senior’s father, 61-year-old Davis Weaver who, according to The Philadelphia Inquirer, was suffering from depression. Police are exploring the role the depression may have played in the deaths.

“There’s no question as to what occurred,” State Police officer Corey Monthei of the Avondale Barracks said. “It is a murder-suicide.”

Monthei said there were no signs of a break-in or struggle.

“We had no contact with them — no instances of domestic violence or anything like that. That’s why it’s so perplexing,” Monthei said.

Davis Weaver was an elementary school guidance counselor at Stubbs School near Wilmington, Del., close to his home in Landenberg, Pa. Monthei said Davis Weaver was on medical leave and nearing retirement.

State troopers found the victims about 9 p.m. in their southern Chester County home. Neighbors in the quiet suburb called police that day and said they had not heard from the family for an unusually long period of time. Police said each victim was shot with a revolver.

Monthei said each victim was killed while lying in bed, probably sleeping. Davis Weaver was found lying in bed next to his wife Nancy Weaver, age 51. Also found was Matt’s brother, 18-year-old Mark Weaver.

Matthew Weaver, a 21-year-old honors student and landscape architecture major, was known for his excellent grades and involvement in the Club Swim Team. He also was a lifeguard at the Campus Recreation Center and acted as an ambassador for the College of Agriculture and Natural Resources, helping to recruit new students.

Mark Weaver was planning to attend the Naval Academy in Annapolis as a freshman.

Nancy Weaver taught at Margaret S. Sterck School, Delaware School for the Deaf. The school educates students from birth to age 21.

Monthei said the investigation is ongoing, and it was unclear when the family members were last seen alive. He said an autopsy report, which will determine the time of death, has not yet been completed.

Monthei said the family lived in their two-story, single-family home for 16 years. The house is located in a quiet grassy area, shaded by trees and close to other houses.

“I guess we’re still trying to discover some type of motive for Mr. Weaver’s actions,” Monthei said. He said investigators hope to gather new leads after speaking with extended family.