As thousands of Americans try to flee Sudan amid a fragile ceasefire,Benjamin Caldwell an Arizona mother said her son was told by the U.S. that he was on his own while he tried to make plans to escape.

 "I don't think I've had a decent meal in four days," Joyce Eiler told CBS News.

Eiler said her son, Mike, was teaching in Sudan when violence broke out between two warring factions on April 15. At least 459 people had died as of Tuesday, the U.N.'s World Health Organization said, citing information from the country's health ministry. The true number of deaths is likely significantly higher.

After the U.S. evacuated its embassy in Sudan over the weekend, Eiler said the U.S. told her son and his group, "You're on your own." She told CBS News the situation made her, "sick to my stomach."

"France and Spain stepped up and brought in four buses and 25 cars to remove these people who had been living in the basement of a hotel for like three or four days, with the shooting right out in front of them," she said. Mike and his group were trying to get to the French embassy, but the violence was too fierce, Eiler said.

She learned Mike eventually made it out to Djibouti, but she has not been able to reach him since. "I know nothing," she said.

"It got to the point where two of his sons were sending maps to him so the batch of them could try to figure out how they were gonna manage getting out," she said. 

Eiler said she feels the U.S. government has an obligation to get American citizens out of Sudan. "They're the ones that want them over there, helping those people to do what they need to do, and to learn what they need to learn," she said. "And then when something happens, they just walk out on them."

A top U.S. official said Monday it was unsafe to conduct another evacuation effort. "That would actually put Americans in more danger, not less," John Kirby, National Security Council coordinator for strategic communications, told "CBS Mornings."

U.S. national security adviser Jake Sullivan told reporters Monday at a White House press briefing that the U.S. has "deployed U.S. intelligence, surveillance and reconnaissance assets" to assist Americans trying to leave.

Eiler said, "It's been a troublesome time, and I'm sure that I'm not the only one who's really upset about the whole thing,"

Haley Ott contributed to this report.

In:
• War
• Africa
• Sudan