Seven people have been killed after a gunman opened fire at a birthday party at a trailer park in Colorado. The dead included the gunman, who killed six people before turning the gun on himself. It is understood that the suspected shooter was the boyfriend of one of the victims. However, the motive for the attack, which happened just after midnight, is unknown. "The tragic shooting in Colorado Springs is devastating, especially as many of us are spending the day celebrating the women in our lives who have made us the people we are today," said Colorado's governor, Jared Polis. It is the second mass shooting in Colorado in a matter of months. On March 22, 10 people were killed in an attack at a supermarket in Boulder. This was the fourth major shooting attack in the US over the weekend. It follows the killing of three people in Baltimore, another three people being injured at a shopping mall in Aventura, Florida, and a toddler being injured in an incident in New York City's Times Square. Idaho school shooting: 'Absolute blessing' no one dead after young schoolgirl opens fire on classmates More than 700 people have been shot or injured in shooting incidents since President Joe Biden took office. Last month Mr Biden used his executive powers to tighten controls including banning stabilising braces which enable guns to be fired more accurately. He has urged Congress to take stronger measures including reimposing a ban on assault weapons which lapsed in 2004 and strengthening background checks.