Two people were killed and four others have been injured as a result of a string of package bombings throughout the Austin, Texas area. Both federal and local law enforcement believe the explosions [VIDEO] are connected in some way and believe they are dealing with a "serial bomber." Since March 19, four explosions have happened in the Austin, Texas area. Two were hours apart from each other on March 12.

Two of those killed include a 39-year-old and 17-year-old kid.

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Among those seriously injured include a female in her 40s and a 75-yea-old woman. Austin Police have confirmed that there are similarities among the package bombs, causing them to believe they are all related.

Package bombings continue to rip through Austin neighborhoods

The first bombing was on March 2, at 6:55 a.m. near Haverford Drive. Police confirmed that a 39-year-old Anthony House was the first victim. The second explosion was on March 12, around 6:45 a.m. around Oldfort Hill Dr. This explosion killed a 17-year-old boy and seriously injured a woman in her 40s. The third explosion happened on Galindo Street, sending a 75-year-old woman to the hospital with critical and possibly life-threatening injuries. The most recent incident was on Sunday, when trip wire that was connected to a "For Sale" sign was set off.

Federal agencies including the ATF, FBI and the U.S. Postal Inspection Service have launched an investigation, alongside local police. The FBI has launched a joint task force. Austin Police Chief Brian Manley said during his press conference that there is no known victimology or ideology that they can connect the bombings to, so they are unable to determine a motive for these serial bombings.

Texas Governor Greg Abbott has issued a $15,000 reward for information leading to the identification and arrest of anyone involved in the serial bombings. Those with tips have been asked to call Texas Crime Stoppers at 1-800-252-TIPS (8477). These are the five things you need know about the Austin package bombings.

1. If you are not expecting a package, do not open it

NBC News has said that Austin Police have told residents to be aware of their surroundings and to report anything that appears to be suspicious, especially an unexpected package. Chief Manley even said that if you receive a package that you are not expecting, or that looks suspicious, do not open it, and instead call 911. While it may take a while for law enforcement to arrive, they have enough law enforcement in the area to allow them to respond to and handle the situation.

On Twitter, Chief Manley said that the three package bombs were made in cardboard boxes.

However, he pointed out that an explosive device of any kind can be hidden in different ways. Manley did not say any specifics about the packages and bombs, because of the ongoing status of the investigation. Manley has not used the serial bomber label.

Austin Police have been stretched thin because of the massive SXSW event, which wrapped up on March 18, and even received a suspicious threat that shut down one planned concert featuring The Roots. Chief Manley said it is time to be vigilant and come together as a city and community and solve this.

2. House was killed in the explosion that occurred early on March 2 at his home

Police have confirmed that Anthony Stephan House, 39, was the first victim killed by the original explosion at his home on Haverford Drive. The explosion occurred at around 6:55 a.m. Police have said the device was “powerful” and caused major damage to the front porch of his home.

House was later rushed to the hospital, where he died. Manley said the death was originally ruled a suspicious death but now they are investigating it as a homicide. Manley says they are looking at the incidents as being related. House worked at several major companies in the Austin area including as a project manager for Texis Quarries since 2016, but has also worked on commercial projects including Toyota One’s North American headquarters in Plano.

3. Second explosion caused severe damage to home where church-going family lives

Police said that the second explosion caused severe damage to a house on Oldfort Hill Drive. The home was a single-family home and was damaged by a package bomb that was placed on the porch. Manley said that a resident brought the package inside and opened it, which caused the injuries, resulting in the death of the young man and serious injuries to the female. Law enforcement will not release the identities of the victims of this explosion.

4. Multiple people called 911 following the third explosion

The Austin Police Department confirmed that 911 dispatchers received multiple calls following the third explosion, which sent a 75-year-old woman to the hospital with life-threatening injuries. One woman who was also present during the explosion was checked out by a doctor, but received no injuries.

This explosion occurred right after Manley and FBI officials held a briefing at the scene of the March 12 bombing. Manley and others left the briefing and headed for the scene of the second explosion, which was on Galindo Street. The Washington Post reported that the latest explosion was set off by tripwire. The tripwire was anchored to a "For Sale" sign and was left on the side of the road. Manley says this technique shows a higher level of sophistication and higher level of skill.

5. Police are not ruling out the possibility of a hate crime

During a press conference streamed on Twitter following the second explosion. Chief Manley told the media and public that he will not put up with this in our city and that Austin has the full support of federal agencies in helping to resolve this major crisis as quickly as possible. Manley has not been able to provide a motive but did say that the victims of the first two explosions were African-Americans and the third was Hispanic, so he would not rule out the possibility of a hate crime. Manley also said that they are not sure if the victims are the intended targets -- it's possible that the packages were left at the wrong address.