Her purse was found the next morning.
At that point, it was obvious she hadn't run off with a lover.
By midweek, her disappearance had already sparked one of the largest investigations in McAllen-area history.
Seventy sheriff's department posse members scoured the region on horseback looking for her body. Sixty-five National Guardsmen were called in. Investigators followed dozens of leads, most pointing toward ex-boyfriends, unrequited admirers or transients.
Skin divers dragged irrigation canals. They just dragged the wrong ones.
On a balmy Thursday morning, four days after Easter Sunday, Irene's body rose to the surface of the Second Street Canal and was spotted by several passersby.
Frightened valley residents began locking their doors. The search switched to a manhunt. There was a murderer on the loose.
In the days after Irene's disappearance, investigators learned of an attempted sexual assault three weeks earlier inside another Catholic church in Edinburg, a nearby town in the valley. Again, the victim, Maria America Guerra, was a young Hispanic female.
Investigators quickly linked the two attacks. And investigators in the Garza case began digging deeper for information on the Edinburg attack.
They re-interviewed the victim. She repeated that her assailant was a white male with horn-rimmed glasses in a light-tan shirt and dark trousers — clothing, she assumed, was that of a priest.
At the time, police were looking for a serial rapist who seemed to lurk around valley Catholic churches preying on attractive young light-skinned Hispanic women. Perhaps the rapist was masquerading as a priest?
The same day Irene's body was found, police investigating the Edinburg case made a stunning discovery:
The priest who last saw Irene Garza alive not only was at the Edinburg church the day of the earlier attack, he matched the victim's and another witness's description of the attacker.
As police continued to publicly state they had no hard leads, they quietly began zeroing in on Father John Feit.
Catholic leaders dreaded the possible fallout if one of their own was the culprit. Not only would it bring scandal to the church, it would give fodder to already deep prejudices within the Protestant community.
Bridges between Anglos and Hispanics, Protestants and Catholics, were just beginning to be built in earnest in deep south central Texas (Irene Garza was seen as an ambassador in that effort).
The investigation of Feit would be kept as quiet as possible.
After Irene's body was found, police spoke again with Feit's supervisor, Father Joseph O'Brien from Sacred Heart Church in McAllen — who admitted something he had kept quiet from police:
Feit was his prime suspect, too.
Maria America Guerra had returned home in the late afternoon of March 23, 1960, after attending classes at Pan-American College.
At 4:30 p.m., the pretty, light-skinned 20-year-old had gone to the outdoor bathhouse behind her home in Edinburg to get cleaned up.
As she walked outside, she noticed a man watching her from a parked car adjacent to the bathhouse, which sat directly across from Sacred Heart Church in Edinburg.
In her April 1960 statement to police, Guerra described the young man as having black hair and horn-rimmed glasses.
He was sitting in a blue-and-white 1955 or 1956 model car.
Later, after dinner, Guerra said she left the house to go across the street to pray in the church.
As she left, she noticed the same car parked between her house and the church. The man with the horn-rimmed glasses was not in the vehicle.
She entered the church through the main doors and walked to the communion rail.
"As I entered the church, I noticed a man sitting alone in one of the rear benches on my left," she said. "This man also had black hair and horn-rimmed glasses, and the thought that it was the same man that I saw earlier entered my mind. But being in a house of God, I dismissed any thoughts of foul play."
Another lady was in the church praying as Guerra knelt to pray. That lady, whom Guerra did not know, soon stood and left the church.
Moments later, Guerra said, she heard the footsteps of someone coming from the back of the church toward the front.
"I looked to see who it was and noticed that it was a man, the same man sitting at the rear of the church when I entered. I noticed that he was wearing a light beige T-shirt and black pants."
Guerra said the man walked to a side door, looked out in both directions, then quickly walked back in her direction.