UVALDE, Texas -- A criminal investigation in Texas over the hesitant police response to the Robb Elementary School shooting is still ongoing as Wednesday marks one year since a gunman killed 19 children and two teachers inside a fourth-grade classroom in Uvalde.
The continuing probe underlines the lasting fallout over Texas' deadliest school shooting and how the days after the attack were marred by authorities giving inaccurate and conflicting accounts about efforts made to stop a teenage gunman armed with an AR-style rifle.
The investigation has run parallel to a new wave of public anger in the U.S. over gun violence, renewed calls for stricter firearm regulations and legal challenges over authorities in Uvalde continuing to withhold public records related to the shooting and the police response.
MORE: Uvalde families frustrated and continue to mourn nearly 1 year after the school shooting
Here's a look at what has happened in the year since one of America's deadliest mass shootings:
A damning report by Texas lawmakers put nearly 400 officers on the scene from an array of federal, state and local agencies. The findings laid out how heavily armed officers waited more than an hour to confront and kill the 18-year-old gunman. It also accused police of failing "to prioritize saving innocent lives over their own safety."
All of the students killed were between the ages of 9 and 11 years old.
At least five officers who were put under investigation after the shooting were either fired or resigned, although a full accounting is unclear. The head of the Texas Department of Public Safety, Col. Steve McCraw, put much of the blame after the attack on Uvalde's school police chief, who was later fired by trustees.
McCraw had more than 90 of his own officers at the school -- more than any other agency -- and has rebuffed calls by some Uvalde families and lawmakers to also resign.
SEE ALSO: ABC News crew spends year in Uvalde, documents journey of survivors, families of shooting victims
Uvalde County District Attorney Christina Mitchell said last week that Texas Rangers are still investigating the police response and that her office will ultimately present the findings to a grand jury. She said she did not have a timeline for when the investigation would be finished.
On Monday, Uvalde Mayor Don McLaughlin said he was frustrated by the pace of the investigations a year later.
"They don't have answers to simple questions they should have," McLaughlin said of the families.
Calls for gun control intensify
President Joe Biden signed the nation's most sweeping gun violence bill in decades a month after the shooting. It included tougher background checks for the youngest gun buyers and added more funding for mental health programs and aid to schools.
MORE: Uvalde families get a win on gun control at Texas state Capitol
It did not go as far as restrictions sought by some Uvalde families who have called on lawmakers to raise the purchase age for AR-style rifles. In the GOP-controlled Texas Capitol, Republicans this year rejected virtually all proposals to tighten gun laws over the protests of the families and Democrats.
Republican Texas Gov. Greg Abbott has also waved off calls for tougher gun laws, just as he did after mass shootings at a Sutherland Springs church in 2017 and an El Paso Walmart in 2018. The issue has not turned Texas voters away from Abbott, who easily won a third term months after the Uvalde shooting.
The Uvalde school district permanently closed the Robb Elementary campus and plans for a new school are in the works. Schools in Uvalde will be closed Wednesday.
WATCH: Slain Uvalde girl dreamed of Paris: How a photojournalist helps her spirit live on in City of Lights
About a dozen students in the classroom where the shooting unfolded survived the attack. Some returned to class in person last fall. Others attended school virtually, including a girl who spent more than two months in the hospital after being shot multiple times.
Veronica Mata, a kindergarten teacher in Uvalde, also returned to class this year after her 10-daughter Tess was among those killed in the attack.
Some Uvalde families have filed lawsuits against the gun maker and law enforcement.