By Faith Karimi and Jason Hanna, CNN

(CNN) -- A suspect in a wave of bombings that terrorized Austin killed himself with an explosion inside his car as authorities closed in, police in Texas said, ending a manhunt but leaving investigators scrambling to determine whether any bombs remain and if he acted alone.

The 24-year-old man detonated the bomb early Wednesday on the side of Interstate 35 in Round Rock, north of Austin, as SWAT team members approached him, police said.

Investigators believe he is responsible for the five explosions that killed two people and injured five others in Austin or south-central Texas since March 2, authorities said.

They also warned a wary public not to let down their guard just yet.

"We don't know where this suspect has spent his last 24 hours, and therefore we still need to remain vigilant to ensure that no other packages or devices have been left throughout the community," Austin Police Chief Brian Manley said.

Latest developments

• The suspect is white, Manley said, without naming him or saying where he lived.

• Surveillance video shows this man, wearing gloves and a cap, taking two packages into a FedEx store in the south Austin area, Mayor Steve Adler said. CNN affiliate WOAI published those surveillance images, which the station said were recorded Sunday.

• Authorities determined in roughly the past two days that this person was someone of interest and believed by late Tuesday that he was the prime suspect, Manley said.

• Surveillance teams tracked the suspect's vehicle to a hotel in Round Rock, about 20 miles north of Austin. As police waited for tactical units, the vehicle left the hotel, Manley said.

• SWAT members approached the vehicle, and the suspect detonated a bomb, killing himself and knocking back and injuring a SWAT member, Manley said.

• A SWAT officer fired his weapon at the suspect, Manley said. It's not clear whether the officer shot him.

• Police don't yet "understand what motivated him to do what he did," Manley said.

• "This investigation is still underway, so we cannot say that this was individual acting on their own," Manley said.

• President Donald Trump tweeted: "Austin bombing suspect is dead. Great job by law enforcement and all concerned!"

FedEx blast

In the last attack before the suspect's death, a package exploded early Tuesday at a FedEx sorting center near San Antonio. A second unexploded bomb was discovered hours later at another FedEx facility near Austin.

Those two packages were connected to four previous bombings that left two people dead, law enforcement agencies said Tuesday evening. FedEx said the person who sent the package that exploded Tuesday also shipped a second one that was turned over to law enforcement officials.

FedEx also said it provided authorities with "extensive evidence" from its security system on the packages and the person who shipped them.

In the incident near San Antonio, the device detonated on an automatic conveyor, said Michael Hansen, police chief in the city of Schertz. A female employee was treated on site. The FedEx facility was not the intended target, Hansen said.

The investigation

As investigators search for a motive and possible accomplices, they are checking camera footage from the facilities connected to Tuesday's incidents, a federal law enforcement source said.

Investigators believe the same person is behind all the explosive devices, the source said, adding that the devices are similar in design and use the same components, including a "mouse trap" or a "close pin" switch, according to the source.

"We made one to show everyone what it looks like, and we did it in an hour," the source said. The bombmaker may have taken longer to build the devices to avoid blowing himself up, the source said.

The level of bombmaking skill doesn't necessarily point to military experience, the source added.

Investigators said the package that was found intact Tuesday may yield some clues.

"Now we have the blueprint and possible DNA on the inside of the bomb. So, teams are working to render it safe and then look for DNA," the source said.

The outside of the package would have been touched by shipping store employees and by the bombmaker, the source said. The bombmaker may have worn gloves.

The explosions

The first three explosions in Austin involved cardboard packages left in front yards or on porches. The parcels weren't delivered by the US Postal Service or services such as UPS or FedEx, police have said.

Those blasts -- one on March 2 and two more on March 12 -- killed or wounded three African-Americans and one Hispanic person. They happened in east Austin areas where most residents are minorities, and some there expressed concern the attacks might have been racially motivated.

The first explosion killed 39-year-old Anthony Stephan House; the second killed 17-year-old Draylen Mason; and the third critically injured a 75-year-old woman. Police have not ruled out the possibility that those bombings could be hate crimes.

In the fourth blast, on March 18, a device was triggered by a tripwire, injuring two white men in an area where most residents are white.