The clues all came together to where Mr. Conditt was on Wednesday morning, in the darkened parking lot off Interstate 35.

The showdown started with an apparent mistake.

At one minute past 4 p.m. on Tuesday, paramedics were notified about an “unknown medical alarm” at Mr. Conditt’s home in Pflugerville. Two paramedics from the Pflugerville Fire Department responded. A person inside the home — it was unclear whom — answered the door and told the medics no one there had called 911. The paramedics cleared out at 4:11 p.m.

From an incident report released Friday by the Pflugerville Fire Department, it now appears that a request by investigators for paramedics to remain near the house was relayed instead as a call for immediate medical aid to the residence. It is possible that Mr. Conditt himself had come to the door or was home at the time, and began to suspect that the authorities were closing in.

Finding paramedics at his door could have been the reason Mr. Conditt drove to Round Rock and appeared to be taking steps that signaled he knew the police were on his trail. At some point in the hours to come, he left a roughly 25-minute recording on his phone that officials described as a confession. Law enforcement officials said the miscommunication involving the paramedics was under review.

Closing In

On Tuesday night, investigators were still sorting through a multitude of tips and blind alleys.

The local, state and federal agents hunting the bomber wondered if he had struck again. About an hour after the paramedics had left Mr. Conditt’s residence in Pflugerville, the team of investigators had converged on a Goodwill store in south Austin shortly after 5 p.m. in response to a report of an explosion. That incident ended up being unrelated: Military-style ordnance that someone had donated had ignited and injured a worker. It took attention away from Mr. Conditt.

But not for long. Later that evening, the police closed Main Street in Pflugerville.

It was not until later that they traced his vehicle to the Courtyard by Marriott in nearby Round Rock. When Mr. Conditt pulled his Pathfinder out of the parking lot, a stream of vehicles slowly followed. Mr. Filla, the deputy marshal, described it as the opposite of a high-speed chase. Agents, he said, were hoping to capture Mr. Conditt alive and avoid any harm to themselves.

Using what he described as a “tactical vehicle maneuver,” the SWAT team managed to cautiously push Mr. Conditt’s vehicle onto the edge of a service road just off Interstate 35. Officers approached the vehicle, but were stunned by an explosion triggered by Mr. Conditt as they moved in.