A 24-year-old man was found guilty of involuntary manslaughter in the death of an elderly Thai man whose 2021 killing in San Francisco helped spark a national movement against anti-Asian American violence.

A jury did not find Antoine Watson guilty of murder when it returned a verdict on Thursday for the January 2021 attack on 84-year-old Vicha Ratanapakdee. Jurors found Watson guilty on the lesser charges of involuntary manslaughter and assault.

The office of the San Francisco district attorney, Brooke Jenkins, declined to comment, saying that the jury was still empaneled. Jurors will return on 26 January to hear arguments on aggravating factors, and sentencing will be scheduled once that is completed, the office said in an email.

Ratanapakdee was out for his usual morning walk in the quiet neighborhood where he lived with his wife, daughter and her family when Watson charged at him and knocked him to the ground. The encounter was captured on a neighbor’s security camera. Ratanapakdee died two days later, never regaining consciousness.

His family says he was attacked because of his race, but hate-crime charges were not filed and the argument was not raised in trial. Prosecutors have said hate crimes are difficult to prove absent statements by the suspect.

Watson testified on the stand that he was in a haze of confusion and anger at the time of the unprovoked attack, according to KRON-TV. He said he lashed out and didn’t know that Ratanapakdee was Asian or elderly.

The San Francisco public defender, Mano Raju, whose office defended Watson, extended his sympathies to the victim’s family and said the defendant was “fully remorseful for his mistake”.

“While this death was a terrible tragedy and has garnered a lot of press attention, the importance of our legal system is that it gives us a chance to look at the facts in a balanced way,” he said in a statement.

Hundreds of people in five other US cities joined in commemorating the anniversary of Ratanapakdee’s death in 2021, all of them seeking justice for Asian Americans who have been harassed, assaulted and even killed in alarming numbers since the start of the Covid-19 pandemic.

Asians in the US have long been subject to prejudice and discrimination, but the attacks escalated sharply after the coronavirus first appeared in late 2019 in Wuhan, China. More than 10,000 hate incidents against Asian Americans and Pacific Islanders were reported to the Stop AAPI Hate coalition from March 2020 through September 2021.

The incidents involved shunning, racist taunting and physical assaults.