4th victim found dead after a mass shooting at a Fourth of July block party in Shreveport, Louisiana

A fourth victim has died after a mass shooting at a Fourth of July block party in Louisiana, Shreveport police and a city council member said.

"Last night was a horrible night here in Shreveport," Police Chief Wayne Smith told reporters Wednesday.

At least 11 people were shot during the melee around 11:40, police said.

Among the seven who were shot and survived, one was in critical condition and six had suffered non-life-threatening wounds, Shreveport police spokesperson Sgt. Angie Willhite said.

Police initially said three victims were killed, but later said a fourth person was found dead Wednesday. The fourth victim was discovered in an area with tall grass and dense vegetation, Shreveport District A Councilwoman Tabatha Taylor said.

Taylor said officials are hoping to get a drone in the air to continue searching for other possible victims.

"It's believed that multiple males engaged in an exchange of gunfire," Smith said.

It's not clear what led up to the gunfire, which shattered a "family and community event" that had safely taken place for more than a decade, Taylor said.

No suspects have been arrested, and the slain victims have not been publicly identified by police.

It was difficult for first responders to get to the victims due to the number of vehicles at the gathering, police told CNN affiliate KSLA.

"Getting here and getting EMS here was a difficult thing. A lot of us had to park our cars and take off running because there were so many cars on the side of the street," Shreveport police Lt. Van Wray told KSLA.

With a potentially large number of witnesses, Taylor implored anyone with information to call police, even anonymously.

"I am looking for justice for these families," the councilwoman said. She said the assailants "have traumatized us in a way that is unfathomable."

The tragedy in Louisiana was among a spate of mass shootings across the country over the Fourth of July weekend.

In Baltimore, at another block party on Sunday, two people were killed and another 28 were shot and injured - mostly teenagers. Investigators are searching for multiple assailants.

In Philadelphia, five people, including a 15-year-old boy, were killed Monday night. Authorities said the shooter appeared to fire randomly along several blocks of the city's Kingsessing neighborhood before officers arrested the suspect, who was found with an AR-style rifle and a handgun.

In Texas, three people were killed and eight others were wounded in Fort Worth late Monday night - hours before the neighborhood's Fourth of July parade took place on the same street.

And in Washington, DC, nine people were injured - including two minors - shortly before 1 a.m. Wednesday. Someone from a vehicle "fired shots in the direction of some of our residents that were outside just celebrating the Fourth of July," Metropolitan Police Assistant Chief Leslie Parsons said.

Across the country, at least 412 people have been killed in mass shootings so far this year, according to the Gun Violence Archive. Like CNN, the nonprofit defines mass shootings as those in which four or more people are shot - not including the perpetrators.

CNN's Jeremy Grisham contributed to this report.