The man who plowed his car into a crowd of people in New York’s Times Square Thursday was charged with murder, attempted murder and vehicular homicide after he killed one person and left another 20 injured. Richard Rojas told police he had taken drugs prior to the incident.

Initial reports speculated that Rojas, 26, had taken K2, or synthetic marijuana. But Rojas told police he had actually taken PCP.

“I smoked marijuana,” Rojas told officers, according to a court document. “I laced the marijuana with PCP.”

Marijuana laced with PCP would likely have had effects similar to that of synthetic marijuana. In security footage from the incident, Rojas could be seen driving his car in a controlled manner before seemingly waiting for cars to pass and speeding the wrong way down the street into a crowd of people. 

RTX36GNF A vehicle that struck pedestrians and later crashed is seen on the sidewalk in Times Square, New York City, May 18, 2017. Photo: Reuters

Rojas’ Bronx neighbor said he hadn’t been the same since he came back from serving in the United States Navy. 

“He was into a lot of military stuff,” Harrison Ramos told CBS News. “That’s why he joined, that’s why he served his country. He loved his country. But he just didn’t come back the same.”

Addiction medicine expert and founder of the Center for Network Therapy Dr. Indra Cidambi said undiagnosed post-traumatic stress disorder or some sort of other mental illness combined with synthetic drugs could have explained why he seemed to be driving so normally before the incident. PCP could have caused his symptoms to be exacerbated or triggered, spurring his actions.

“PCP is going to cause psychosis,” she told International Business Times in an interview Friday. “So if the marijuana was laced with it, we can expect the person to exhibit psychosis. Being a veteran, if there was underlying PTSD or he had been exposed to certain traumatic events in the past, he could have gotten triggered when he saw the crowd of people there.”

“I wanted to kill them,” Rojas told police at the scene. Rojas killed 18-year-old Alyssa Elsman and left another 20 people injured, some in critical condition, when he drove his car into the crowd Thursday.

Cidambi explained that PCP can cause homicidal thoughts that the drug user then acts on.

“If he was driving normally up until he saw the crowd, he could have been triggered and have had homicidal thoughts that intensified or had a flashback from the past that he reacted to when he saw the crowd,” she said. “Having an underlying homicidal thought is quite common when you do this drug.”

RTX36FUS An injured man is seen on the sidewalk in Times Square after a speeding vehicle struck pedestrians on the sidewalk in New York City, May 18, 2017. Photo: Reuters

Rojas had been arrested twice in New York for drunk driving: once in 2008 and again in 2015. He also plead guilty to drunk driving, failure to pay a just debt, drunk and disorderly conduct and communicating a threat during his time in the military in 2013.

“[Rojas] demonstrated mental health issues going back to childhood [that] went unaddressed even during the time he was in the military,” New York City Mayor Bill de Blasio told WNYC Radio Friday.  “It appears to be intentional in the sense that he was troubled and lashing out. At the root of this is an untreated mental health issue going back probably decades.”

Rojas also had a history of substance abuse, according to reports.

“I’ve seen people who have PTSD as an underlying disorder abuse these drugs because they think it’s going to make them less anxious,” said Cidambi. “But underneath it actually intensifies the PTSD, the flashbacks and the paranoia.”

The symptoms exhibited by Rojas at the time, including slurred speech and glassy eyes, were consistent with those that would be seen in someone who had taken PCP or synthetic marijuana, Cidambi noted.

“At the end of the day, it alters your mind,” said Cidambi. “And it’s deadly.”

RTX36G3D An injured woman is seen at a crosswalk in Times Square after a speeding vehicle struck pedestrians on the sidewalk in New York City, May 18, 2017. Photo: Reuters