Two people went on a shooting spree in Las Vegas on Sunday, killing two police officers and one civilian before taking their own lives.

The incident began at CiCi's pizza when a man and a woman walked in and shot police officers Alyn Beck, 42, and Igor Soldo, 32 who were eating lunch at the restaurant chain.

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Reportedly, one of the officers was able to fire back before he died, but it remains unclear if either suspect was hit, Sheriff Doug Gillespie of the Las Vegas Metro Police Department said at a news conference Sunday afternoon.

Eyewitnesses said that when the shooters walked into the pizza restaurant,  one of them yelled "This is a revolution," before the two opened fire. The suspects then fled to a Wal-Mart across the street.

According to police reports, the two perpetrators shot a civilian and yelled at everyone to get out of the store. They then ran to the back of the Wal-Mart where they shot and killed themselves. 

According to reports, the female shooter took her male companion's life before turning the gun on herself.

"It's a tragic day," Gillespie said. "We have a community to protect, we will do it with our heads held high."

Las Vegas police stated that they don't know anything about the shooters and have not yet pinpointed a motive for the crime.

The case is considered extremely complex as it involves more than 1,000 witnesses. Wal-Mart employees and shoppers were taken to a nearby clothing store to be interviewed after the incident, but it is unclear whether or not eyewitnesses from CiCi's have been held for questioning.

This is only one in a series of shootings to strike a nation harassed by gun-related violence. Most recently, a shooter opened fire at Seattle Pacific University, killing one before being disarmed by students.