Editor's note: This story has been updated to reflect the execution.

HUNTSVILLE — A hit man for the Mexican Mafia gang was executed Wednesday night for the 1998 strangling death of a San Antonio woman, becoming the fourth inmate to face lethal injection in Texas this year.

Manuel Vasquez was declared dead at 6:32 p.m., 17 minutes after a lethal dose of pentobarbital was released through an IV into his arm. He was sentenced to death for his role in the murder of Juanita Ybarra, 51, who had refused to pay gang members a 10 percent street tax on illegal drugs she was selling.

Asked if he had a last statement, Vasquez, strapped onto a gurney, looked straight up at the ceiling and uttered a brief one.

"I want to say 'I love you' to all my family and friends. Thank you, Lord for your mercy and unconditional love. In Jesus' name I pray, amen," Vasquez said. His sister, Mary Helen Vasquez, cried loudly as she watched her brother take about two dozen breaths before becoming unconscious.

She declined to make any statement following the execution.

In 1999, jurors convicted Vasquez after hearing how he, Johnny Joe Cruz and Oligario Lujan, broke into Ybarra's motel room and beat up her boyfriend before turning on Ybarra, who Vasquez strangled with a telephone cord. Prosecutors say Ybarra was killed after refusing to pay a street tax to the gang.

The trio robbed the couple of their valuables and left. According to court records, the three were working for Mexican Mafia boss Rene Munoz, who was on the Texas Department of Public Safety's 10 Most Wanted List until his 2012 arrest. Cruz took a plea deal and served seven years. Lujan is serving a 35-year prison term.

Court records show Vasquez had a history of violence. He received a 10-year prison sentence for his role in the 1986 death of Robert Alva, who was beaten, choked and set on fire.

The execution of Vasquez leaves the Texas Department of Criminal Justice with enough pentobarbital — the drug it uses for lethal injections — for one more execution, unless a new supply of the drug is found. Six more executions are scheduled between now and mid-May.

Jason Clark, spokesman for TDCJ declined to elaborate specifically on what options the state's prison system is considering if a new pentobarbital source is not found.

"I can't speculate on that," he said. "We are exploring all options including the conitnued use of pentobarbital or an alternative drug or drugs."

Vasquez' execution is the 522nd in Texas since the state reintroduced capital punishment.

On March 18, Randall Mays is set to die for fatally shooting two police officers in Henderson County, and he is expected to be the last to be put to death with pentobarbital, the one-drug method used by Texas since 2012.

In September 2013, TDCJ turned to compounding pharmacies, which are allowed to mix or "compound" drugs on site, for its lethal injection drugs after manufacturers stopped providing pentobarbital to U.S. prison systems. But this week, the state prison system confirmed it only had enough pentobarbital for the Vasquez and Mays executions.

While prison officials will not say if they plan to move to another drug combination, TDCJ has been buying midazolam since 2013 and has 40 vials on hand that have yet to expire. However, the drug is at the center of a legal challenge from Oklahoma inmates now before the U.S. Supreme Court. A ruling is expected in late May.