Oklahoma man Ruben Armendariz, 28, murders his ex-wife and three children aged 2, 5 and 9 before turning gun on himself in horrific murder-suicide

Tributes have been paid to an 'amazing mother' who was shot and killed by her ex-husband - who also murdered their three children before turning the gun on himself.

Police say Ruben Armendariz, 28, gunned down Cassie Flores, 29, at her home in Oklahoma City on Wednesday night.

He then shot their three children, Hillary, 9, Damaris, 5, and Matis, 2, before shooting himself at around 11pm.

Emergency services rushed to the scene, and found five people injured, rushing Armendariz and one of the children to hospital where they were pronounced dead.

The couple had been married, but had separated, though it is unclear if Armendariz was living with his estranged wife and children at the time.

Police say Ruben Armendariz, 28, gunned down Cassie Flores, 29, (pictured) at her home in Oklahoma City on Wednesday night

He then shot their three children, Hillary, 9, (left) Damaris, 5, (right) and Matis, 2, (center) before shooting himself at around 11pm 

Cops are still investigating the motive behind the killing, saying in a statement: 'This investigation is in the very early stages.

'Detectives are currently trying to piece together the chain of events that led to the massacre'.

Tributes to the mother and her three children have flooded in, with her family describing the situation as a 'nightmare'.

Flores' sister, Rocio, posted pictures of her loved ones online, writing: 'I can't believe this. My babies and my sister. They are all gone this feels like such a nightmare.

'I didn't get to say goodbye to them, and I feel such a guilt in my heart that I can't stand.

'God is with us and he will never leave our side. Fly high my babies fly high my beautiful angels.'

Officers confirmed that they had not been called to a domestic disturbance at the home before the fatal incident.

Armendariz's only prior history appeared to be a traffic violation in 2020, where he was convicted of driving without a valid license.

Emergency services rushed to the scene, and found five people injured, rushing Armendariz and one of the children to hospital where they were pronounced dead

Tributes to the mother and her three children have flooded in, with her family describing the situation as a 'nightmare'

Cops are still investigating the motive behind the killing, saying in a statement: 'This investigation is in the very early stages'

Officers confirmed that they had not been called to a domestic disturbance at the home before the fatal incident

Sgt. Gary Knight added: 'They're still trying to figure out what led up to this.

'Sometimes we just never know. Nobody seems to have seen it coming. If they did, no one alerted us.'

The Western Heights School District wouldn't confirm which, if any, of the victims attended their schools but added counsellors are on hand if needed.

Anyone with information on the shooting is urged to call the Homicide Tip-Line at 405 297-1200.