A shooting that erupted in a Houston park over the weekend that left a pregnant woman dead and four other people injured marked the 400th mass shooting in the United States in 2023, according to a national website that tracks firearm deaths and injuries.

The Houston incident was among six mass shootings that occurred on Saturday and early Sunday in cities across the nation, according to the Gun Violence Archive, which defines a mass shooting as a single event with four or more victims either injured or killed.

With a little over five months still to go in the year, the number of mass shootings is up 9% from 365 mass shootings that occurred as of this time in 2022 -- a year in which a total of 647 mass shootings unfolded, according to the Gun Violence Archive.

The Houston shooting happened just after 1 a.m. on Saturday at Margaret Jenkins Park in the southern part of the city as a birthday party was ending, police and witnesses said. Killed in the shooting was a 21-year-old woman, identified by her family as Autumn Vallian.

Vallian's mother, Ebony Vallian, told ABC station KTRK in Houston, the shooting occurred as she and her daughter were attempting to leave the party when at least two people engaged in an argument, pulled guns and started shooting.

"I looked back and my baby was down on the ground. Gone," Ebony Vallian said. "I lost my baby. She was in school, trying to get a job, trying to become something, and she's gone now."

ShotSpotter gunfire detection technology in the area recorded 36 gunshots fired in the incident, which left four other people wounded, according to the Houston Police Department.

Two suspects in the shooting were among those hospitalized with gunshot wounds, police said.

The Houston incident was among six shootings across the nation over the weekend in which four or more people were wounded or killed.

Early Sunday, four people were shot in Seattle at an illegal street racing event, according to police. The shooting, which according to the Gun Violence Archive is the 401st mass shooting this year, occurred in the city's Capitol Hill neighborhood around 4 a.m., and left two women and two men hospitalized, including one with critical injuries, police said. No arrests were immediately announced.

At least five people were shot, one fatally, in the Parkway Village Section of southeast Memphis around 4 p.m. on Saturday, according to the Memphis Police Department. One of the victims critically injured in the shooting was a child, police said.

No arrests were announced in the Memphis shooting.

In Wade, North Carolina, about 12 miles northeast of Fayetteville, one person was killed and three others were shot around 1 p.m. on Saturday during what police described as a "physical disturbance" at a gas station. No arrests were announced.

Four people were shot and wounded outside a hotel in Glendale, Arizona, Saturday morning, according to police. The shooting erupted about 2:15 a.m. as officers responded to an unrelated call and heard gunshots coming from the parking lot of a Renaissance Hotel, authorities said. No arrests were announced.

In Chicago, a 40-year-old man was killed and three other men were wounded during a shooting that occurred at 12:13 a.m. on Saturday in the city's North Lawndale neighborhood, according to the Chicago Police Department. The victims were standing on a sidewalk when two men walked up and opened fire, police said. No arrests were announced.

Saturday's shooting was the third mass shooting in Chicago this month, according to the Gun Violence Archive. On July 5, a man was killed and five other people were wounded when gunfire broke out at a Fourth of July gathering outside a residence in the city's Englewood neighborhood, police said. On July 16, one person was killed and four others were wounded in a drive-by shooting in Chicago's Garfield Park neighborhood, according to police.

Eleven other cities have had two mass shootings in July, including Philadelphia, Baltimore, Cleveland, Houston, Dallas, New York, Memphis, El Paso, Texas; Fort Worth, Texas; Lansing, Michigan and Shreveport, Louisiana, according to the Gun Violence Archive data.

July has been a particularly violent month in the United States with 65 mass shootings claiming the lives of 81 people and leaving 300 wounded, according to the website's data.

Twenty-two of the mass shootings in July occurred over the extended Independence Day weekend, leaving 22 people dead and 126 injured, according to the website.

One of the deadliest Fourth of July weekend shootings unfolded in the Kingsessing neighborhood of Philadelphia, where a man armed with an AR-15-style rifle, a pistol, extra magazines and wearing a bulletproof vest and a ski mask, allegedly went on a rampage, firing at least 50 shots randomly at victims, killing five, including a 15-year-old boy, and wounding two other children, according to police.

Kimbrady Carriker, 40, the suspect in the Philadelphia shooting, was arrested and charged with murder and attempted murder. He has yet to enter a plea to the charges.

On July 2, a Fourth of July weekend block party ended in a mass shooting that left 2 people dead and 28 injured in the Brooklyn Homes neighborhood in the southern district of Baltimore, according to police. A 17-year-old boy suspected of being one of multiple shooters in the incident was arrested on July 7 and charged with possession of a firearm by a minor, possession of an assault weapon, reckless endangerment and possession of a handgun in a vehicle.

The Baltimore mass shooting remains under investigation and more arrests are expected, police said.