A neighbourhood in Austin, the capital of Texas, U.S. has been put on lockdown after a fourth bomb went off on March 18 injuring one person. The first three bombs, spread out over the first two weeks of March have claimed two lives and injured another three. Today’s victim is said to be in a serious but stable condition.

Austin police have now said the four explosions that have rocked the city are believed to be the work of a single ‘serial bomber’.  The police have concluded this due to the timing and similarities in the device used in the attack. This, despite the fact that the location and the detonation method of today’s attack is a change to the three previous incidents. “We are clearly dealing with what we expect to be a serial bomber at this point,” Brian Manley, the police chief, told reporters on Monday.

All the victims of the previous three incidents picked up packages left on their doorsteps that exploded; the package that killed the teenager detonated in his kitchen. Today’s attack was triggered by a trip wire connected to a fence on a road in a residential community.

The police have begun exploring possible connections between the victims. Anthony House, 39, died on 2 March. Then 17-year-old Draylen Mason was killed on the morning of 12 March and his mother was hurt. About five hours later, Esperanza Herrera, 75, was seriously injured. The two who died were African American and their families know each other, raising suspicions of a racially motivated attack.

Because the victims have been from the African American community and the attacks took place in the east of the city which is home to the city’s black and Hispanic population, the NAACP, the civil rights organization, on Monday called the bombings acts of domestic terrorism. The New York Times reported the victims who were killed belonged to African-American families with deep roots to the city's Black, religious and civil-rights groups. Community leaders in Austin have said the first victim Anthony Stephan House, was the stepson of Freddie B. Dixon, a retired United Methodist minister and a civil rights advocate while Draylen Mason, was the grandson of Norman L. Mason, a prominent dentist in the community.

The NAACP’s demand is being supported by three members of the Congressional Black Caucus who on Monday called for the bombings in Austin, Texas, to be classified as "Ongoing terrorist attacks… We also call on the chairmen of the committees we serve on -- Homeland Security and Judiciary -- to recognize the gravity of the domestic terrorism threat and work with us on developing concrete and common-sense solutions to counter it. For too long we have focused only on certain sources of terrorism and violence while ignoring others," the statement added.

But the police chief of Austin is not willing to classify the attack even as a hate crime. “We are not willing to classify this as terrorism, as hate, because we just don’t know enough. And what we have seen now is a significant change from what appeared to be three very targeted attacks to what was last night a target that would have hit a random victim that happened to walk by,” Brian Manley said.

The frequency of the attack has pushed the U.S. government into sending a massive force of FBI officials to investigate the explosions. Reports suggest that anywhere from 350-500 FBI investigators have joined the probe in Austin and the agency has posted a monetary reward for anyone who comes with concrete information of the bomber. But, it remains to be seen if another attack will take place with police swarming all over the city and if the attack will be categorized as an ‘act of domestic terrorism.’

(The above story first appeared on LatestLY on Mar 20, 2018 09:39 AM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website latestly.com).