A manhunt is underway for the sniper who shot a sheriff's deputy Wednesday afternoon in the parking lot of a Los Angeles County Sheriff's Office.

Deputy Angel Reinosa, 21, is lucky to be alive after his bullet proof vest deflected the bullet from his chest to his shoulder when the gunman opened fire around 2.45pm. He suffered a 'very minor' wound.

Two shots rang out from a four-story apartment building that houses the mentally ill located just a block from the sheriff's station, Los Angeles County Sheriff's Capt. Todd Weber said.

The Arbor Fields apartment building where the shooter is believed to have fired from is adjacent to and, partners with, a nonprofit that provides housing, counseling and other services to people with mental health issues, according to the website for Mental Health America, Antelope Valley Enrichment Services.

The nonprofit said several housing units are 'designated specifically for individuals with disabilities ... who are ready for independent living.'

Trainee sheriff's deputy Angel Reinosa, 21, was shot in the parking lot of a LA County Sheriff's Office Wednesday afternoon

A manhunt is underway for the sniper who is believed to have fired from the third or fourth floor of a nearby apartment building in the Lancaster neighborhood

Graphic shows from where the bullets were believed to have been fired , according to information gathered from reports

Reinosa is a rookie who has been with department for a year and came to the Lancaster station for training in May.

The captain said he was leaving for the day, heading to his personal vehicle and about to take the bullet proof vest off when he was struck.

A Sheriff's Department source said the gunman fired two high-velocity rifle rounds - one of which 'grazed' the injured deputy's right shoulder, The LA Times reports.

Reinosa's ballistic vest deflected the bullet from his chest into his shoulder.

'He is doing great, thankfully,' Weber said. 'The wound was minor and he's been treated and he's doing well, in high spirits.' No surgery was needed, he added.

Police had no description of the shooter but believed they could narrow down the area of the building where the attacker might be, Weber said.

Deputies searched for the sniper inside the block-long, four-story structure with many windows that overlook the sheriff's facility in downtown Lancaster, a desert city of about 160,000 people north of Los Angeles.

Tactical teams were working their way through the building Wednesday night, evacuating some people and having others shelter in place, Weber said.

Lancaster Mayor R. Rex Parris (pictured) said he was outraged that a housing complex that houses the mentally ill was so close tot he sheriff's station

Lancaster Mayor R. Rex Parris expressed his outraged that the housing complex was placed so close to a sheriff's station.

'It's not just a four-story apartment building; it's a four-story apartment building that is government-subsidized for mentally ill people,' he said.

'Why do you put mentally ill people in a four-story building across from the Sheriff's Department? It's indefensible and something has to be done about it.'

The mayor said it appeared that the shooting was a random act.

'It was not targeted on this specific deputy,' he said. 'It was, 'any deputy would do.''

The Arbor Fields apartment complex where the shooter reportedly fired from houses people who suffer from mental illness

There are believed to be 99 apartments within the Arbor Fields building which, according to the local mayor, houses and gives counselling to people with mental health illnesses.

Immediately after the shooting, a SWAT team locked down the Lancaster neighborhood and entered the apartment complex where the suspect is believed to have fired from a third or fourth floor window.

Other deputies were also fired on shortly before 3pm local time but escaped uninjured, Deputy Morgan Arteaga of the Sheriff's Information Bureau said.

Deputies set up a perimeter at the location, 501 West Lancaster Boulevard, adding that the suspect was armed and not yet in custody, CBSN Los Angeles reports.

More than two dozen police vehicles scrambled to the scene, which is also within yards of senior citizen housing, an elementary school and a church.

'The deputy was walking out of a building and a sniper took a shot at him. It is incomprehensible that this kind of thing is happening in our city.

'We are blessed that nobody was killed. It is a difficult situation.'

A motive for the attack is not yet known.