In scenes mirrored across the country, thousands mourned George Floyd and marched against racism and police brutality in Houston, where he was raised and buried. Among the demonstrators was the city’s police chief.

Art Acevedo has attracted attention as an outspoken advocate for change after the killing of Floyd, a black man who was filmed gasping for breath under the knee of a white Minneapolis officer.

Acevedo has a substantial platform as the chief of police in the fourth-largest US city and the president of the Major Cities Chiefs Association, covering the US and Canada.

“Policing, as imperfect as it is today, it is absolutely ages better than it was 34 years ago, but we’ve still got work to do,” Acevedo told the Guardian this week. “We have to look at the court system, we have to look at the prosecutors, we have to look at the prison system, we have to look at probation, parole, at the entire criminal justice system.”

Critics accuse Acevedo of grandstanding for the cameras. He says his background as an immigrant from Cuba gives him deep empathy for communities of colour, and he has long acknowledged the need for transparency, accountability and reforms of use-of-force policies.

Surrounded by protesters last month, voice cracking, forefinger jabbing, he launched a broadside against racists.

“We built this country. I’ve got news for them. We ain’t going nowhere. We ain’t going nowhere… So if you’ve got hate in your heart for people of colour, get over it. I’m here to tell you we will march as a department with everybody in this community. I will march until I can’t stand no more.”

Donald Trump, meanwhile, urged governors to “dominate” protestors.

“Let me just say this to the president of the United States on behalf of the police chiefs in this country,” Acevedo told CNN in return. “Please, if you don’t have something constructive to say, keep your mouth shut. It’s not about dominating, it’s about winning hearts and minds.”

Acevedo told Texas Monthly in February he is a lifelong “Rino”, a Republican In Name Only, disillusioned by a lack of compromise between parties focused on their bases. Last year, he assailed the GOP establishment’s fealty to the National Rifle Association.

“I don’t want to see their little smug faces about how much they care about law enforcement when I’m burying a sergeant because they don’t want to piss off the NRA,” he said of senators stalling the reauthorisation of the Violence Against Women Act after an officer was killed while responding to a domestic violence call.

‘It was important to be out there’

Acevedo was born in Cuba in 1964 and moved to the US as a refugee aged four. He grew up in California and started out 34 years ago as a highway patrol officer in East Los Angeles. When he became the chief of police in Austin, in 2007, his progressive stances seemed a good fit, though that department has problems with racism and excessive use of force that belie the city’s liberal image.

Acevedo took charge in Houston in 2016, becoming the first Hispanic chief in a “minority-majority” city of 2.3m people. About 45% of the population are Hispanic, 23% are African American and 7% are Asian.

“Being the target of discrimination as a child and even as a member of the California highway patrol, I felt it was important to be out there and mourn the loss of George Floyd with our community,” he told the Guardian.

“I’m the leader of the department and so if they’re angry with our department I’d rather they vent with me than at my young officers who had nothing to do with what happened in Minnesota. Then that venting turned into mourning, and mourning together.”

Some activists have accused Acevedo of failing to practice what he preaches, pointing to a corruption scandal in the narcotics squad and six fatal police shootings in five weeks, including the April killing of Nicolas Chavez, a 27-year-old in an apparent mental health crisis who was on his knees when multiple officers fired.

Cellphone footage captured the shooting but images from police body cameras have not been released. Acevedo said the situation was complex and he did not want to risk compromising investigations.

“I am completely committed to transparency but transparency has to be done and handled in a manner where you don’t jeopardise accountability, because process matters,” he said. “Once everything’s done, where we know we’re not going to jeopardise any outcome, I will absolutely release everything that the public wants to see.”

Cities nationwide are grappling with how to enact police reform. This month the Houston mayor, Sylvester Turner, signed an executive order banning chokeholds and requiring de-escalation techniques. It legally codified some practices which were already department policy, and more reviews are planned.

But campaigners were frustrated when the city council voted to increase the police budget by $19m to $964m. Turner, who is black, argued that under-resourced neighbourhoods want a greater police presence.

Austin is poised to take a more radical approach that includes diverting funds to other public services. Acevedo is convinced there is national support for systemic transformation though it is doubtful whether major shifts are realistic while Trump is in the White House.

“I’ve got to hang on to hope,” he said, “because I think that at some point political instinct would hopefully kick in and he’ll come to the realisation that this is something that the American people across the political spectrum want addressed.

“I really believe there’s a great awakening going on here as it relates to racial inequities, discrimination, racism, economic inequities. I really believe this is something we’ve never experienced and I think that as a result we’re going to see a collective effort of the American people and a collective demand like we’ve never seen for justice, equality, inclusion and equal opportunity.

“This is a watershed moment like I’ve never seen.”