An Oklahoma Man Lost His Son. A Day Later, He Drove Onto a Crowded Sidewalk.

The Moore police chief, Todd Strickland, said Mr. Townsend showed signs of being intoxicated during a field sobriety test. The police obtained a warrant to draw his blood and were awaiting the results of toxicology tests from the Oklahoma State Bureau of Investigation.

Sergeant Lewis said Mr. Townsend, who does not live in Moore but has relatives in town, had previous arrests for driving under the influence, drug possession and leaving the scene of an accident.

In the moments after the crash, students helped point the police in the direction of the fleeing vehicle, called 911 and began performing CPR on their classmates before teachers and emergency personnel arrived. The force of the impact threw Ms. Martinez, the student who later died, over a fence and into a school duck pond. Her classmates jumped into the pond to pull her out.

“The students rose to the challenge,” Robert Romines, the superintendent of Moore Public Schools, said in an interview. “After that, teachers and coaches rose to the challenge.”

Four of the students who were struck by the pickup were set to sign cross-country scholarships for college on Wednesday, including Rachel Freeman, the senior who died at the scene.

“We have students with broken hearts,” Mr. Romines said. “We had adults who have broken hearts. This is a struggle. Schools across the state are offering help to answer the call.”

Moore High School is one of the largest high schools in Oklahoma, with about 2,500 students on a sprawling, 80-acre campus. The school had been reeling from another fatal crash weeks earlier, in December. In that case, an 18-year-old student, Emily Gaines, was killed in Oklahoma City after her S.U.V. was hit by a speeding car driven by an off-duty Moore police officer. Ms. Gaines, a senior, had been heading to take the ACT, a college entrance test. The officer, Kyle Lloyd, has been charged with first-degree manslaughter.

Kolby Crum, a senior who was injured in Monday’s sidewalk crash, was in critical condition on Tuesday, officials said. Joseph White, a senior, and Shiloh Hutchinson, a junior, remain hospitalized. Ashton Baza, a sophomore, was released after sustaining a broken leg and broken ankle, the authorities said.

Ben Fenwick reported from Moore, Okla., and Manny Fernandez from Houston.