Texas Teen Kills Mother, Two Neighbors Before Taking His Own Life: Police

On Friday, a Texas teenager allegedly killed his mother and two of his neighbors before committing suicide, police tell PEOPLE.

Authorities in Uvalde, Texas, received a call on Friday from a man who told dispatchers he watched a young man – later identified as Dylan Westerburg, 19 – shoot his friend, 58-year-old Arthur Jerome Norton.

The witness told officers he fled Norton's home after his friend was shot, and heard more rounds being fired as he sprinted away.

Officers arrived at Norton's home and "announced themselves," according to police. Next, police claim they heard a single gunshot, which led to an hours-long standoff that ended on Saturday.

That final shot, police believe, was Westerburg taking his own life.

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During the standoff, officers worked to evacuate nearby homes, and while searching one residence, located the body of Westerburg's 42-year-old mother, Jennifer Diane Jacques.

Police tell PEOPLE that Jacques had sustained a single gunshot wound and was found on the floor next to her dog, which had been shot to death.

When they entered the residence on Saturday, police found the bodies of Norton; his 60-year-old brother, Phinny Paul Norton, and Westerburg.

A possible motive for the killings remains under investigation, police tell PEOPLE.

Efforts to reach relatives of the victims were unsuccessful Monday and several neighbors reached by phone declined to comment.