SAN ANTONIO -- A father whose son went missing in 2011 took the stand Wednesday in the federal trial of an alleged war commander for Los Zetas drug cartel.

The defendant in this case is Mariano Millan-Vasquez, known to everyone as "Chano." Multiple witnesses have testified that Millan-Vasquez controlled the region of Piedras Negras for Los Zetas and is responsible for hundreds of killings and disappearances.

Former Zetas members testified Tuesday, claiming the cartel is responsible for a bloody massacre in Piedras Negras in 2011.

On Wednesday morning, prosecutors called Jaime Abascal Reyna to the stand. The last time Reyna saw his son was September 11, 2011. He said that they spoke over the phone every day. When Reyna didn't hear from his son for several days, he started making calls.

Reyna discovered that his son's co-worker and girlfriend were also missing. He was told to contact someone in Los Zetas to see if they had information. The cartel member he spoke with was Jose Luis Rodriguez.

On Tuesday, Rodriguez testified about a bloody massacre involving over 300 people. He said that the Zetas commanders ordered the killings because there was a government informant in the group. They ordered the informant be killed along with anyone and everyone associated with him.

Rodriguez said that when he asked a commander about Reyna's son who disappeared, the commander said for him to stop asking about it, because they just finished "cooking him".

Reyna never heard back from the cartel, so he said that he contacted the Mexican government.

"[The government] told me not to go asking questions about my son. They told me to stop doing that," Reyna said in court.

During a particularly emotional testimony on Wednesday, a former worker for Los Zetas said that he was kidnapped twice by the cartel and was forced to witness several violent acts.

At least two jurors broke down in tears as they listened to Jorge De Leon Navarro describe how Los Zetas killed their prisoners.

De Leon said that he didn't voluntarily start working with the cartel; he was kidnapped and forced to participate.

"The first time [I was kidnapped], they took me with a group of about seven people. They picked us up and told us we had to work for someone, for Los Zetas,” De Leon said in court. “The first one they asked, he didn't want to work, and [cartel members] said, ‘that's fine.’ He turned around, and they shot him in the head. The rest of us agreed."

De Leon said that he helped Los Zetas stash drugs, transport firearms and deliver marijuana to drug mules along the river to be smuggled to the U.S. He claimed that the drugs came from the Zetas "comandantes" or commanders, which included Millan-Vasquez.

When prosecutors asked if De Leon feared police while en route to deliver firearms to "Chano," he said that he wasn't worried because the majority of police were bought out. He said that officers escorted him to remote locations to deliver guns to Millan-Vasquez on more than one occasion.

On July 12, 2012, authorities seized over 50 kilograms of marijuana at the Del Rio port of entry. The load belonged to De Leon.

The witness said that the commanders kidnapped him and his two superiors until they paid what they owed for the seized load of marijuana. De Leon said that his two superiors were let go after they paid, but that he didn't have the $100,000 the cartel needed. He said that cartel members kidnapped him again and held him captive for 13 days until he found the money.

De Leon said that during his captivity, he witnessed Zetas commanders dismember people while they were still alive and throw the body parts into a flaming barrel. He claimed that he was blindfolded, handcuffed, driven to random locations around Piedras Negras, stripped of the blindfold, and forced to kneel and watch these brutal murders.

"They did this so I would tell my family if they didn't obtain the money, this would happen to them," he said in court.

Jurors broke down in tears when De Leon described a mother and father being pulled by their hair and forced to watch their 6-year-old daughter dismembered alive before they faced the same, brutal death. De Leon said that Millan-Vasquez would smile and laugh as he performed these killings.

De Leon said that his mother sold her house for $20,000 to help him, and that the Zetas let him loose with the stipulation that he must pay $100,000 more in one week.

On March 13, 2013, De Leon and his father were apprehended by Border Patrol agents about three miles from the border near Comstock, TX. The two claimed credible fear, telling agents that they feared for their lives if they were to stay in Mexico.

A red Blackberry phone belonging to De Leon was examined by computer forensics experts with Homeland Security Investigations. They recovered deleted material, which included death threats from the defendant and information regarding Zetas operations. De Leon is now cooperating with authorities.

De Leon will serve time in jail after pleading guilty to a marijuana charge.

When prosecutors asked De Leon if "Chano" was in the courtroom, the witness stood up and scanned the courtroom for close to three minutes, before pointing at Millan-Vasquez.

Prosecutors asked De Leon why it took him so long to point out the defendant.

"I'm afraid for my family," he replied.

Millan-Vasquez faces multiple charges, including conspiracy to distribute narcotics, enticing minors to sell drugs, giving a false identification to authorities, and charges for at least nine murders in South Texas and Northern Mexico.

Prosecutors will not seek the death penalty.