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Two people were killed and at least four others injured in a shooting at the Grey nightclub in the German city of Konstanz, July 30, 2017. In this photo, police officers are seen in the streets of Heidelberg awaiting the arrival of the Duke and Duchess of Cambridge on the second day of their visit to Germany in Heidelberg, Germany, July 20, 2017. Getty Images

Two people including the gunman were killed and at least four others were left wounded after a man opened fire in a German nightclub Sunday (Saturday night in the U.S.), police said.

The 34-year-old suspect opened fire at Grey nightclub on Max-Stromeyer-Strasse in the city of Konstanz around 4:30 a.m. CEST (10:30 p.m. EDT). Later the attacker was shot and fatally injured by the police in a gunfight.

The 34-year-old attacker "was critically injured in a shootout with police officers as he left the disco, and later succumbed to his wounds in hospital," according to a press release by authorities after the incident.

Read: Cincinnati Cameo Nightclub Shooting Update: Liquor License Lost After 1 Dead, Multiple Injured

"The motives of the probably only acting man are not yet known. Investigations by the prosecutor's office and the criminal investigation department continue," the release said.

The gunman was said to be an Iraqi national who resided in Germany, Fritz Bezikofer from the Kostanz police told CNN. A German police spokesman told broadcaster N-TV the attacker had lived in the country for a long time and was not an asylum seeker.

"According to our investigations this is not terror-related, unless the gunman radicalized himself within the last three days," Bezikofer said. "At this moment we believe that he may have had alternative motives," Bezikofer added.

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One police officer was also injured during the gunfight with the attacker outside the club. A bouncer at the scene who tried to stop the suspect was also injured. Police authorities mentioned that special commando forces and a police helicopter were deployed in the city as they were not yet sure if the suspect was acting alone or had accomplices, according to BBC News.

The shooting came just two days after a knife attack in the northern port city of Hamburg. A 26-year-old Palestinian killed one and injured six others when he went on a stabbing spree in a supermarket. Investigators said his motives remained unclear; however, he was a known Islamist who suffered from several psychological complications, according to Sky News.

Nightclub shootings have become common and a matter of concern in the United States too. In March this year, one man was killed and at least 15 other people were injured at the Cameo nightclub in Cincinnati, Ohio after a gunman opened fire in the club. More than one gunman was involved in the shooting, according to the Cincinnati police. The club owners had voluntarily surrendered their liquor license after the incident.

One of the worst mass shootings in the history of U.S. took place on June 12, 2016, in an Orlando nightclub where a gunman opened fire early morning, killing 49 people and injuring another 53. The attacker, Omar Mateen shot and killed party-goers at the Pulse nightclub in Orlando with an assault rifle. He fired over dozens of rounds and even took some people hostage. The gunman had pledged allegiance to the Islamic State group (ISIS), according to the authorities.