What you need to know about the Texas biker gang shooting

• Town rallies around student told to remove American flag
• Senior prank involving pineapples takes over yearbook
• GoPro's CEO loses $229M to fulfill promise to college roommate
• Mother's lip-sync of daughter's tantrum is Internet sensation
• Frequent tanner shows graphic skin cancer selfie

A deadly shootout erupted between rival motorcycle gangs at a Twin Peaks restaurant in Texas on Sunday, the Austin American-Statesman reports.

>> PHOTOS: Mugshots from biker gang arrests in Waco, Texas

What happened? The shooting occurred at the Twin Peaks restaurant just after 12:15 p.m. Sunday during a "Bike Night" event police had sought to shut down, the American-Statesman reports. A fight – reportedly over a parking space – began in a bathroom at Twin Peaks and then moved into a crowded bar area, police said. When it spilled out into the parking lot, fistfights turned into armed encounters with bikers eventually firing more than 100 shots, police said. As police neared, bikers turned their sights on officers and exchanged fire with them. Officials said threats have been made against law enforcement agencies in the area after 18 officers from the Waco Police Department and four from the Texas Department of Public Safety returned fire during the shootout.

Nine people were killed and 18 injured. No police were hurt, and it was unclear who killed whom, police said. Police originally said 192 people were arrested, but authorities later revised that number to 170, according to the American-Statesman. Bail was set as high as $1 million for each suspect, as authorities considered pressing capital murder charges against them. Police said they expect to make more arrests in the coming days. Click here to see the mugshots of those taken into custody so far.

Who was involved? The Waco Tribune-Herald reported that multiple law enforcement sources said the Bandidos and Cossacks biker gangs were at the center of the incident, according to the American-Statesman. The Bandidos were listed as a "Tier 2" gang in a Texas Department of Public Safety report on gang activity in Texas. They are known to operate in the Waco area as well as Williamson County, the report states. DPS did not list the Cossacks in the 2014 report.

Who is involved in the investigation? Law enforcement from local, state and federal agencies – including the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives – are assisting in the investigation, the American-Statesman reports.