A 3-year-old San Leandro boy was shot in the head Wednesday night after attending a memorial service for a homicide victim in Oakland, authorities said.

The shooting occurred just before 9:40 p.m. in a residential neighborhood on the 1600 block of 80th Avenue, said Officer Johnna Watson, a spokeswoman for the Oakland Police Department.

Investigators determined that a bullet struck a vehicle that the boy was in and fragments from the bullet caused an injury to his head and face, Watson said.

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The boy and his family were attending a memorial service for 18-year-old Derick Alexander, killed June 27 outside a mini-mart on 89th Avenue and MacArthur Boulevard, about a mile away from the Wednesday night shooting, Watson said. The boy, his mother and an aunt were in the car when gunshots rang out, he added.

“A round struck the vehicle. Metal from the round ended up injuring the child, causing an injury to the face,” said Deputy Chief LeRonne Armstrong.

The boy, who was not identified, was transported to Children’s Hospital and is listed in stable condition.

Mayor Libby Schaaf, who was attending a separate event Thursday at the Oakland Zoo, became emotional talking about the boy’s injuries and said she remains vigilant about making Oakland safe.

“Whenever a child, especially as young as a 3-year-old, is hit by a bullet, it hits all of us,” Schaaf said. “We all are very thankful that the child will recover from the physical injuries caused by the shooting last night, (but) no one, particularly this child, is likely to recover from the trauma for a very long time.”

Armstrong and several other police officials visited the hospital on Thursday to drop off a teddy bear for the boy, who was asleep.

“He’s resting,” Armstrong said. “Of course, it’s been a long night for him, which is understandable. We spoke to his mom for a little bit and put the teddy bear next to him.”

No arrests were made, and there was no suspect information immediately available.

Authorities were planning to review surveillance camera footage.

It’s unclear if the shooting was targeted, police said.

“Our investigators are looking into the connection between all of our shootings,” Armstrong said. “We don’t know if the shooting was connected at all to the actual memorial.”

The number of homicides in Oakland decreased slightly, by about 8 percent, in the first six months of 2018 compared with the same time last year. But since the end of June, an uptick in shootings has caused concern for the Police Department and the mayor.

“We always approach summer knowing that the hot weather and out-of-school time often brings increases in bad decisions and increases in crime,” Schaaf said. “So, I am very concerned. We have had many all-hands meetings around what has been a disturbing recent trend.”

On Tuesday, a man was shot and killed in a residential neighborhood at about 9:45 p.m. on the 900 block of Willow Street. The victim was the city’s 34th homicide for 2018.

Late Sunday, George Reed, 35, of Oakland, was shot and killed in a separate incident, Watson said.

Just hours earlier on Saturday, 24-year-old woman Kadeja Tidwell was killed in a shooting in the area of 102nd Avenue and International Boulevard, according to the Alameda County coroner’s office.

The Police Department has added more officers to patrol the streets, particularly in areas most impacted by violence, Armstrong said.

Schaaf said the city is also increasing violence prevention measures that include street outreach workers, life coaches and holding events like midnight basketball.

“We are obviously concerned at the increase in shootings,” Armstrong said. “We are doing everything we can in order to address these issues.”

The Police Department and Crime Stoppers are offering a $5,000 reward for anyone who has information on the shooting of the 3-year-old that leads to an arrest.

Anyone with information can contact authorities at 510-238-3426 or leave a tip at 510-777-8572.

Kimberly Veklerov, Sarah Ravani and Megan Cassidy are San Francisco Chronicle staff writers. Email: kveklerov@sfchronicle.com, sravani@sfchronicle.com, megan.cassidy@sfchronicle.com Twitter: @KVeklerov @SarRavani, @MeganRCassidy