Monica Spear, a former Miss Venezuela, was shot dead Monday night
Investigators believe robbery was the motive in the slayings of Spear, estranged husband
Their 5-year-old daughter survived with a bullet wound in her leg
Venezuela is one of the world's most violent countries, according to the United Nations
Caracas, Venezuela (CNN) -- In one of her last Twitter posts, Venezuelan beauty queen Monica Spear wished her fans peace, health and love.
The 29-year-old soap opera star was gunned down with her husband by the side of a country road less than a week later.
Their 5-year-old daughter survived Monday's shooting in Venezuela's Carabobo state, authorities said, but was shot in the leg.
Armed robbers opened fire after the car Spear and her estranged husband, Thomas Henry Berry, were driving in broke down, officials said.
"At the moment the only thing we know is that it is presumed that the motive was robbery," Venezuelan Justice Minister Miguel Rodriguez Torres said. "We are still investigating. There are five people detained who are being interrogated."
Spear was Miss Venezuela in 2004 and represented her country in the Miss Universe pageant the next year.
Her popularity opened the door to acting roles in soap operas that eventually made her an international star. She worked in Colombia and more recently in the United States, where she made her home in Miami.
Word of Spear's slaying spread quickly on social media and drew a massive response from fans in the South American nation and well beyond its borders.
Movie stars, fellow soap opera actors, athletes and government officials expressed sorrow and condemned the attack.
Venezuelan President Nicolas Maduro called the killing a massacre and said more needed to be done to put a stop to violence.
Venezuela is one of the world's most violent countries, according to a United Nations ranking.
One person is killed roughly every 21 minutes in Venezuela. And there were 24,700 violent deaths last year in the oil-rich country of roughly 30 million people, according to the nonprofit Venezuelan Violence Observatory.
"This happens every day in Venezuela. ... If the victim had not been this actress, the person would simply be one more statistic," said Luis Izquiel, a lawyer and criminologist in Caracas.
Richard Linares, Spear's Venezuela-based personal trainer, said the slaying shows how little life is valued in his country.
"Life does not matter," he told CNN en Español Tuesday. "A life can be traded for some shoes."
"It devastates me that there is a 5-year-old girl who is asleep, and when she wakes up she will ask how her parents are, and she no longer has any parents," Linares said.
Venezuelan officials said they're committed to solving the problem.
"It is painful, not only the death of this beloved Venezuelan actress and the wound her daughter received, but also the death of any Venezuelan who falls in the hands of violence," Rodriguez said.
Authorities also said they had assigned two prosecutors to investigate Monday's slayings.
In an interview with The Huffington Post last year, Spear said she left Venezuela because of the country's security problems.
But Spear was eager to visit her home country over the holidays, close friend and CNN Latino anchor Maria Alejandra Requena said.
"She wanted to spend Christmas and New Year's in Venezuela," Requena said, "to travel around Venezuela, to let her little daughter know her country."
Journalist Osmary Hernandez reported from Caracas. CNN's Rafael Romo and Catherine E. Shoichet reported from Atlanta. CNN en Español's Camilo Egaña contributed to this report.