PICTURED: California dentist's receptionist who was shot in the legs by gunman after he opened fire, killing one and striking two, before fleeing in U-Haul

A gunman who opened fire at a southern California dental office, killing one and injuring to others, knew some of the victims, according to police.

Mohammed Abdulkareem, 29, was arrested on Thursday after a desperate hours-long search following the shooting at the Smile Plus Dentistry & Orthodontics on North Magnolia Avenue in El Cajon, a city about 15 miles northeast of San Diego.

The office's receptionist Yareli Carrillo, 28, was shot in the legs but is in stable condition and expected to survive. 

A man in his 40s who has not been named was also injured but expected to survive.

Police have not identified the man killed in the shooting at the office, which is run by the father-and-son team of doctors Jack and Benjamin Harouni. 

The office's receptionist Yareli Carrillo, 28, was shot in the legs but is in stable condition 

Mohammed Abdulkareem, 29, was arrested after a desperate search following the shooting at the Smile Plus Dentistry & Orthodontics in El Cajon 

Images of a SWAT team outside of the El Cajon dental office where a shooting unfolded Thursday afternoon

It's not clear if the Harounis were in the office at the time of the shooting. 

Captain Rob Ransweiler said Abdulkareem was familiar to the people inside the office, as reported by The San Diego Union-Tribute.

'There were a lot of family members on scene,' he said. 

'Most of the people who were involved, they have information as to who was involved.'

Police believe that Abdulkareem, a resident of El Cajon, rented a white U-Haul pickup with an Arizona license plate just an hour before the shooting.

Abdulkareem reportedly used a handgun, but it's not clear how many shots he fired.

The U-Haul was found abandoned shortly before police located the suspect nearby.

Officials are still looking into a motive. 

The office is run by the father-and-son team of doctors Jack (pictured) and Benjamin Harouni

Dr Benjamin Harouni is pictured above. It's unclear if the father and son were in the office when the shooting took place 

The suspect's vehicle, a white U-Haul pickup truck with Arizona license plate AM14894, was identified shortly after the shooting. Police said they then confirmed that the suspect had rented the truck

Police reported that Abdulkareem had been captured just after 10pm on Thursday. He was taken into custody and the firearm has been located. 

Ransweiler briefed the press on Thursday evening and said officers found the victim who died inside the office as the shooting was still going on and took him outside where they could safely perform lifesaving measures. 

The FBI's San Diego team, as well as the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, are aiding the investigation.