During a news conference on Monday, Brownsville Police chief Felix Sauceda told reporters that the suspect, identified as George Alvarez, attempted to flee the scene after hitting 18 people with an SUV on Sunday morning.

At least eight people were killed in the incident, which Sauceda described as “a tragic event”.

“Through the investigation, it was found that the SUV ran a red light, lost control, flipped on its side and struck a total of 18 individuals,” said Sauceda, who added that authorities have not ruled out the possibility that the crash was intentional.

The incident comes amid months of heated rhetoric around immigration and just days before a border restriction known as Title 42 is set to expire, prompting concerns around a possible influx of migrants and refugees at the US-Mexico border.

Sauceda said on Monday that several of the victims were originally from Venezuela, adding that US authorities were communicating with Venezuelan government officials about the incident. All the victims were men, he added.

“We grieve for the victims in Brownsville, Texas, who were run over outside a migrant shelter where people from around the world are seeking asylum and safety,” said Oni Blair, executive director of the American Civil Liberties Union (ACLU) of Texas.

Horrific. We grieve for the victims and for our Brownsville community.

We call on federal, state, and local governments to take immediate action to protect migrants and ensure witnesses can come forward without fear of deportation or reprisals. https://t.co/ifZVCcPIih

— ACLU of Texas (@ACLUTx) May 7, 2023

“We understand the motive is still under investigation,” Blair said in a statement on Sunday. She urged authorities to ensure that witnesses to Sunday’s incident can come forward without fear of retribution or deportation.

“This horrific event comes after weeks of escalating anti-immigrant policy-making by Texas politicians and while the Biden administration considers imposing a new asylum ban aimed at deterring, rather than welcoming, migrants seeking protection.”

A video online purporting to capture the crash shows a speeding SUV ploughing into a row of people sitting on the side of a road. A second video appears to show the aftermath, with victims lying on the ground, some bloodied and writhing, others motionless.

Shelter director Victor Maldonado said the SUV ran up the curb, flipped and continued moving for about 60m (200 feet). Some people walking on the sidewalk about 9m (30 feet) from the main group were also hit, Maldonado said.

Maldonado said the centre had not received any threats before the crash, but it did afterwards. “I’ve had a couple of people come by the gate and tell the security guard that the reason this happened was because of us,” he said.

Luis Herrera, a witness whose arm was hurt in the incident, told the AFP news agency that the crash was “sudden”.

“A woman went by in a car and warned us to get out of the way,” the 36-year-old Venezuelan national said. “It was a matter of moments. The killer came [through] in the car, gesturing at us, insulting us.”

Sauceda, the police chief, said on Monday that the suspect — who faces 10 counts of aggravated assault with a deadly weapon, among other charges — had an extensive criminal history and was being held on $3.6m bail.

Brownsville is one of several US border towns expecting an increase in asylum seeker arrivals when Title 42 expires on Thursday.

The policy, which has been slammed by rights groups since it was first invoked in March 2020, allowed US border officials to rapidly turn away most people seeking protection at the border.

The surge in the number of asylum seekers this past week has prompted Brownsville commissioners to indefinitely extend an emergency declaration during a special meeting last Thursday.

“We don’t want them wandering around outside,” Pedro Cardenas, a city commissioner, said of the asylum seekers on Sunday after the crash. “So we’re trying to make sure they’re as comfortable as they can be so they don’t have to go out and look for anywhere else.”

A vigil will be held at the Texas state Capitol in Austin on Monday evening “to honor the memory of the lives lost in Brownsville and demand an end to policies that dehumanize immigrants”.

Rochelle Garza, president of the Texas Civil Rights Project, an advocacy group, said in a statement on Sunday: “I hope that today serves as a wake up call and that state officials will begin investing in a humanitarian response that might have helped the people who were impacted by this morning’s tragedy.”

In a statement on Monday, the Venezuelan government called for an investigation into whether it was a crime of hate and xenophobia.