The US postal worker who was shot and carjacked of her mail van in a gunman’s wild Texas rampage was identified Sunday as one of the seven deceased victims by her heartbroken twin sister — and the two were on the phone when tragedy struck.

Mary Granados, 29, was near the end of her shift Saturday and chatting with her sister, Rosie, when their conversation was abruptly punctuated by the mail carrier’s terrified scream, the surviving twin told CNN.

“It was very painful. I just wanted to help her and I couldn’t. I thought she had got [bitten] by a dog or something,” Rosie Granados told the network. “I tried calling her name and she wouldn’t answer.”

As Rosie would later learn, her sister had been blasted and carjacked by a gun-toting madman, who used the USPS van to continue a gore-streaked spree that began moments earlier when he shot a state trooper and fled a highway car stop.

All told, the gunman — who has thus far only been identified as a man in his 30s — killed seven people and wounded more than 20 as he drove between Midland and Odessa, where he was ultimately shot dead by cops in a movie theater parking lot.

Granados, an Odessa resident who moved with her family across the border from Juarez, Mexico when she was 14, was remembered fondly by a USPS colleague.

“She was beautiful inside and out, with a great heart and always ready to be a friend,” wrote co-worker Leslie Aide on a GoFundMe page for the benefit on her slain colleague’s family. “[She] always had a smile on her face!”

Leila Hernandez, 15, was also fatally shot and her brother, Nathan, wounded, according to another page on the crowdfunding site set up by the siblings’ family.

Among the wounded victims were three cops — including seriously-injured Midland cop Zack Owens — and 17-month-old girl Anderson Davis, who caught shrapnel to her face and chest.