Butler police on Monday obtained an arrest warrant for a Pittsburgh man accused of firing a barrage of gunshots last week at a house in the 300 block of Wagner Avenue.

Joshua McKenzie, 30, a felon, is charged with two counts of aggravated assault, and illegal possession of a firearm and discharging a firearm into an occupied structure, all felonies.

He also faces two counts of reckless endangerment and a charge of terroristic threats, both misdemeanors.

Police allege McKenzie about 7:40 p.m. Nov. 17 fired eight rounds from a 9 mm pistol into the house occupied by Rainy Rose and Ryan Mullen, neither who live there.

None of the shots hit anyone, but Rose, 30, was struck by flying glass. She was treated at Butler Memorial Hospital for a cut to the back of her head and released, police said.

While Butler police Capt. David Dalcamo has declined to discuss a motive, court documents suggested McKenzie possibly went to the house at 313 Wagner Ave. looking for Mullen, 29, who he believed had tried to rob his girlfriend at gunpoint in 2013.

But investigators apparently have not ruled out a drug-related motive either.

The home, said county Detective Tim Fennell, who heads the Butler County Drug Task Force, is a known “drug house.”

Fennell on Monday acknowledged the house had been under surveillance since September.

“We’ve received a large number of complaints of drug activity there,” he said.

On Saturday, just four days after the shooting, Butler police seized more than 4 grams of crack cocaine packaged for sale at the house, where they had gone hunting a man wanted on unrelated warrants.

While investigating the shooting, police interviewed Rachel Boychuck, McKenzie’s girlfriend, who also lives in the 300 block of Wagner Avenue. She lives there with her 2-month-old daughter.

She told police McKenzie is the father of the child and admitted he had recently been living with her. She characterized the couple’s relationship as “on and off,” according to a police affidavit.

Boychuck, 37, disclosed that her boyfriend is bipolar and that “at any time can snap,” the affidavit said.

Boychuck recounted a short time before the shooting, she went down the street with her baby and spoke to Rose and Mullen, who she did not immediately recognize.

But she soon learned Mullen’s identity. He tried to rob her after she got out of jail in 2013, she told police.

Mullen, interviewed by police, acknowledged he had “done a lot of bad things in the past when he was doing illicit drugs,” documents said.

During that troubled past, he conceded, he may have robbed Boychuck but he could not be certain. Since that time, he claimed, he had “cleaned himself up,” documents said.

Not long after Boychuck and Mullen met on the street, McKenzie appeared outside 313 Wagner Ave., where Mullen and Rose were in the living room, Rose told police.

Rose and other witnesses recounted the suspect started banging on the door. He called for Mullen to come out.

“Ryan, come out here. I’m gonna kill you,” McKenzie yelled, according to Rose’s account.

Moments later, shots rang out. First, McKenzie allegedly shot several rounds in the front door. Then more shots were fired into the rear door.

Rose and Mullen ran for cover, heading into the basement, documents said. She noticed blood coming from the back of her head and wrongly believed she had been shot.

Mullen called 911. Scared neighbors also notified the county’s communication center of the shooting.

Butler police were there quickly. State police Cpl. Timothy Morando said he and other troopers and officers at the barracks heard the radio call and headed to the scene to assist.

Dalcamo said investigators later recovered shell casings from all eight rounds they suspected McKenzie fired at the house.

At least two rounds went through the house before hitting and lodging into the siding of one of the homes next door.

Police eventually went to Boychuck’s house, looking for McKenzie, but he was not there, documents said. She told investigators that McKenzie had called her but he denied shooting at the house.

Meanwhile, Boychuck denied McKenzie was selling drugs while police questioned her why reportedly he had been seen coming and going at the house at 313 Wagner Ave., several times a day, before the shooting.

Court records showed that McKenzie in February pleaded guilty in Butler County to possessing a small amount of marijuana.

In Allegheny County, he has convictions for misdemeanor drug possession in 2004, and for robbery and carrying a firearm without a permit in 2005.

Those felony convictions in 2005, under state law, prohibit McKenzie from ever owning or possessing a gun.