Investigators say they worked with multiple agencies to conduct a thorough investigation and arrest the suspect in Lake Jackson.
Investigators did not immediately say if there was a suspect description or what led up to the shooting of 81-year-old James Blount.
The sheriff's office said the 19-year-old was shot in the head by his 18-year-old friend. Authorities said it's being investigated as an accidental shooting.
The battle over the valedictorian title began in January, when court documents revealed that Nathan Olivarri was named top of the class, but that honor was short-lived.
Authorities said a homeowner called Saturday night, reporting that they had found a unknown dead person in front of their residence.
A 20-year-old man was killed after an altercation at a Humble-area house party with over 100 people in attendance ended in gunfire, according to HCSO.