A crowd of picnickers was sitting on folding chairs on a grass median in Chicago on Saturday, sipping drinks and trading snacks, when a man in a pickup truck stopped to yell that their dogs were misbehaving.

The crowd asked the man to leave, witnesses told the Chicago Tribune. Instead, the man used an anti-Asian slur toward one picnicker, witnesses said — and then rammed his red Ford F-150 into the group, striking two people as others, including a pregnant woman, scrambled to escape, police and prosecutors said.

One 42-year-old woman was trapped under the car and seriously injured, the Chicago Police Department told The Washington Post. “She could have lost a limb or been killed,” attendee Troy Brown told WLS-TV.

On Monday, Timothy Nielsen, 57, was charged with four counts of attempted murder, police said. A judge ordered him held without bail, the Chicago Sun-Times reported.

Nielsen could not be reached for comment as of early Monday. It is unclear whether he has retained an attorney.

Prosecutors on Monday made no mention of Nielsen using anti-Asian slurs during the attack, and police have not said whether they are investigating the incident as a hate crime. But some community members and city leaders are asking authorities to investigate it as such. Chicago, like much of the nation, has battled a recent surge in racist attacks against Asian Americans and Pacific Islanders.

Before the attack on Saturday, Nielsen stopped his truck to tell a neighbor who was watering his flowers that he was bothered by “yuppies on the boulevard out with their dogs,” prosecutors said. He allegedly added, “Watch what I’m going to do,” before speeding down an alley and driving up to the curb where the group was gathered.

It was about 5 p.m. when Nielsen interrupted the group of about 10 people celebrating a birthday party on the median in Logan Square, a northwest Chicago neighborhood where Nielsen has lived for 20 years, said Assistant State’s Attorney Lorraine Scaduto, the Tribune reported.

When the group told Nielsen to leave, he became “increasingly hostile,” Scaduto said. Nick Lau, 33, who was present at the picnic, told the Tribune that he told the driver his “unsolicited comments were unwelcome” and waved at him to leave. Lau, who is Asian American, told the Tribune that Nielsen then yelled an anti-Asian slur, though he said he didn’t remember the exact words. Rob Lopez, another attendee, told Block Club Chicago that he heard Nielsen say “f--- Asians” or “g-----n Asians.”

Moments later, Nielsen drove back several feet, put the truck in drive and then plowed into the crowd, Scaduto said. Initially, only one of his truck’s wheels made it past the curb, so the driver accelerated again before striking two people as others ran to safety.

“He ran over a bike, he ran over a chair, he ran over a couple other bikes, and I didn’t see exactly how he hit the cooler and hit her but she ended up under the vehicle,” Brown told WLS-TV, referencing the 42-year-old woman who was seriously injured.

If it weren’t for a cooler that wedged between the front of Nielsen’s truck and the grass, preventing him from driving further, Scaduto said, the situation would have been even more “disastrous.”

Nielsen allegedly continued revving his engine until the group rushed to remove him from the truck. Then, he brandished a knife at the group, cutting at least one person in the arm, Scaduto said.

The attack ended when a woman who was driving pulled over and stepped in, Scaduto said. She managed to take the knife and the keys from Nielsen and turn his truck off.

Police arrived at the scene around 5:15 p.m. and arrested Nielsen. Lopez, one of the witnesses, told the Tribune that the woman who was stuck under the truck was released from the hospital on Sunday.

Neighbor Vincent Geraghty, who was walking his two dogs when Nielsen allegedly drove into the crowd, told WLS-TV it was clear the driver was attacking the crowd.

“There was no doubt in my mind this person wasn’t trying to back up to get into an open parking spot or anything like that. He literally jumped the curb, aimed at the people and gunned his truck,” Geraghty said.

Nielsen is scheduled to appear in court again on May 10, the Tribune reported.