A member of the police (Front) stands outside a movie theatre where a man opened fire inside a crowded movie theater on Thursday night in Lafayette, Louisiana July 24, 2015.[Photo/Agencies]

A lone gunman opened fire inside a crowded movie theater in Lafayette, Louisiana, on Thursday evening, killing two people and injuring seven others before taking his own life, police said.

The gunfire erupted during a 7 p.m. CDT (0000 GMT) showing of the film "Trainwreck" and took place almost three years to the day after a massacre at a cinema in Aurora, Colorado, that killed 12 people.

Lafayette Police Chief Jim Craft said two people died in the hail of bullets before the 58-year-old suspect killed himself with a handgun as officers rushed to the scene shortly after 7:30 p.m.

Seven people suffered injuries ranging from non life-threatening to critical, Craft said.

Authorities said they knew the gunman's identity but were not releasing his name during the early stage of the investigation. They offered no immediate motive and did not disclose any clues they might have found.

"The shooter is deceased. We may never know," Craft said, adding that the man appeared to have a criminal history that he described as "pretty old."

Police officials said that bomb-sniffing dogs had alerted on a backpack inside the theater and that they had also signaled "suspicious" items inside the suspect's car. A robot was being used to probe the vehicle further.

Investigators also headed to the gunman's home. His body remained inside the theater several hours later. None of the victims, who were described as ranging in age from teens to early 60s, were immediately identified by authorities.

Witnesses said the gunman abruptly stood up in the darkness of the theater about 20 minutes into the movie and began shooting.

"He wasn't saying anything. I didn't hear anybody screaming either," Katie Domingue, who was watching the film with her fiance, told the local Advertiser newspaper.

Republican Louisiana Governor Bobby Jindal traveled to Lafayette, a city of about 120,000 people roughly 55 miles (90 km) southwest of Baton Rouge.

"As governor, as a father and as a husband, whenever we hear about these senseless acts of violence it makes us both furious and sad at the same time," he said at a briefing.

Jindal said that two of the wounded victims were teachers and that one of them managed to pull a fire alarm in the theater after being shot.

The shooting came three years after a gunman opened fire at a movie theater in Aurora, Colorado, during a midnight screening of the Batman film, "The Dark Knight Rises", killing 12 people and wounding 70 others.

James Holmes, a former neuroscience graduate student at the University of Colorado, was convicted last week on 165 counts of murder, attempted murder and explosives in the July 20, 2012, rampage.

Jurors in that case were trying to determine if Holmes should face the death penalty or life in prison during a penalty phase of that case.

The United States has witnessed several mass shootings in the last two months.

A gunman is accused of a racially motivated shooting at a black church in South Carolina that killed nine church members in June. More recently, a gunman attacked military offices in Tennessee last week, killing five US servicemen.

Jindal, who last month announced his candidacy for president, said he had ordered National Guard members at offices and other facilities to be armed in the wake of the Tennessee attack.