Police in Austin have arrested a man after a series of shootings that left six people dead and three people injured, including two police officers and a bicyclist, over the course of eight hours.

Austin’s interim police chief, Robin Henderson, said at a news conference early on Wednesday that the violence occurred in two separate incidents across two central Texas communities. He said police were not aware the incidents were connected until after they arrested the man, named as 34-year-old Shane James.

James is now being held in Travis county jail, charged with two counts of capital murder and, police say, he is the prime suspect in the terror spree.

Henderson said investigators were uncertain if there is any relationship between the suspect and the victims. The suspect has been charged with capital murder, and additional charges are pending, Henderson said.

“I want to emphasize that APD and other law enforcement did not determine that these incidents were connected until the last incident occurred tonight after the male suspect was taken into custody,” Henderson said.

According to the Austin American-Statesman, the city’s police department received the first call for service at 10.40am on Tuesday that a sergeant with the Austin independent school district had been shot in the leg, prompting a lockdown of the school.

Less than two hours later, police responded to a double homicide – a man and a woman – in south Austin.

Then at 5pm, police received a 911 call that a male cyclist had been shot, causing non-life-threatening injuries.

That was followed at 7pm by a call about a burglary. Officers arrived at a home to find the suspect, who shot and wounded one, in the backyard. The police chief said the incident had been captured on body-worn camera by police.

The suspect fled the scene in a vehicle, and was pursued until he crashed at an intersection and was arrested. Officers then checked the house where the burglary occurred to find two people dead inside. Neighbors told the outlet that the man and woman had moved in only a few days ago.

James is also suspected of killing two people whose bodies were found in a small room at a residence that public records show is his home address in San Antonio.

The Bexar county sheriff, Javier Salazar, said his deputies had decided to force their way in when they discovered water leaking from the home and discovered a “pretty grisly crime scene”, reported CNN.

The victims have not been named and police have not indicated any relationship with the shooter.

The US broke its own record for most mass shootings in a single year earlier this week, with a series of murders taking the figure to 38 incidents in which four or more people were shot and killed. The previous high was 36, set last year.