The death toll from a shooting spree in numerous Colorado sites that ended with the gunman being shot dead has grown to five, according to authorities.

The shooting spree began at 5:00 pm Monday and spread to at least four other places in Denver and Lakewood, according to authorities, who had previously announced that the death toll is four.

According to police, two people were slain and a man was injured in the first site in Denver, while another man was shot dead outside his home.

The gunman then went to Lakewood, where he fatally shot another man at the Lucky 13 tattoo studio and wounded another.

Lakewood officers were able to identify the shooter as he switched sites using information acquired from previous assaults.

No motives; a shooting spree

According to authorities, the shooter entered a retail mall and fatally shot a female employee.

In the shopping mall, he was confronted by a police officer who told him to lay his handgun down. The officer was wounded in the ensuing firefight, but the suspect was killed.

Lakewood Police Spokesperson John Romero reported that the gunman was "pronounced dead on the scene." He went on to say that the officer was "doing well", but that she would require further surgery.

The shooter's motivations were unknown, but police said that "based on what we know, it does appear that the offender was targeting specific people." Two weapons were recovered by police.

Gun violence is a major issue in the United States, according to gun control proponents, who say that the issue is exacerbated by the widespread availability of firearms and the country's permissive gun laws.

Earlier, one person was killed and 14 were injured in a shooting in Baytown in the southern US state of Texas, Harris Country Sheriff Ed Gonzalez said.