A New Jersey man went on a killing spree that lasted three months in the fall of 2016.

Khalil Wheeler-Weaver has been accused of murdering three women and attempting to murder a fourth. On Thursday, a day of testimony was filled with evidence about his cell phone searches for date-rape drugs, curiosity about deadly poisons, and pursuit to have sex with women, Yahoo News reports.

Evidence also showed he used his cell phone to study how to create drugs strong enough to knock a person out, and how to kill someone using household chemicals like bleach and ammonia. He tried to figure out how to erase his search history, according to testimony.

Wheeler-Weaver also looked up how to become a police officer, searching phrases like “Police entrance exam practice test.” His stepfather is a police detective, and his uncle is a police officer; Wheeler-Weaver worked at a hotel and grocery store as a security guard.

The crime spree looks to have started on Aug. 31, 2016 when Robin West, 19, a purported prostitute, was last seen. Her body was discovered on Sept. 21 in an abandoned building that had been set ablaze. Wheeler-Weaver cell phone’s location tracking places him at the house right before the fire. After he left, he drove back to watch the firefighters put out the flames.

A second victim, 20-year-old Sarah Butler, was found in Eagle Rock Reservation on Nov. 29, 2016. When Wheeler-Weaver solicited Butler for sex through a social media app, she typed, “Wow,” adding, “You’re not a serial killer, right?” Another victim, 33-year-old Joanne Brown was found dead at a vacant home on Dec. 5.

The fourth woman he was set out to kill, “T.T.” testified in court about her own harrowing experience. She woke up in the back seat of her car with duct tape on her face and was “choked back to sleep.” She eventually persuaded Wheeler-Weaver to take her to a motel and was able to lock herself in a motel room.

Wheeler-Weaver was apprehended on Dec. 6, 2016. While searching his home, police found an additional three cell phones in his bedroom.