The big question being asked is why authorities were unable to prevent the rampage. The local governor says information that forewarned of the attack was not properly shared.
The first warning came months ago. Uematsu wrote a letter to the Speaker of Japan's Lower House in February. It detailed a plan to attack the care home at night and tie up staff members. That's precisely what happened during Tuesday's attack.
Uematsu also told his colleagues at the facility that he thought people with severe disabilities should be euthanized. Those comments led local officials to have him committed to a hospital. But he was released 12 days later, after a doctor decided he was not a threat.
Following his discharge, the care home installed more than a dozen security cameras based on police advice.
Kanagawa Prefecture oversees the facility. The Gov. Yuji Kuroiwa says his office was left in the dark and none of that information was shared with him.
"We believe there have been problems in the way authorities share information. We will cooperate with the authorities concerned so this kind of incident never happens again. We will verify the matter thoroughly in order to develop preventive measures," he says.
The governor said people tend to think the suspect's discharge was too early. But he said holding him any longer would have created a human rights issue. He said he wants to consult with experts on how to best deal with such a situation.
An expert on forensic psychiatry said more information is needed to tell whether proper measures were taken during Uematsu's stay in the hospital.
"It's hard to say at this point whether this incident was preventable or not. I have to say that there was no problem with him being released from hospital because the doctors saw that he was no longer mentally disturbed at that time," Igarashi says.
But he says the problem is that there's no proper follow-up system after such people are released.
"We have to carefully analyze his mental condition and how he was living his life in the period between his release and the attack. And we have to utilize the results to come up with effective measures to prevent this kind of tragedy," Igarashi says.
Families and supporters of people with disabilities are making sure their voices are heard, as the investigation unfolds.
Atsuko Kubo's son, Jusuke, is 41 years old. He is not able to speak and lives in a care facility. She says she was deeply hurt by what the murder suspect was saying, that people with disabilities should disappear.
"Not only is it unforgivable, it makes me sad," Kubo says. "Even though it might only be a limited number of people who think that way, it's the fact that anyone does."
Kubo heads an organization of people with intellectual disabilities. It issued a statement on its website saying each and every life is priceless regardless of its challenges.
People across Japan are expressing support for that through social media. One person wrote "We have to make sure this kind of crime never happens again."
An organizer at one care facility has been trying to create more awareness of and interaction with people with disabilities. Masahiro Tate came up with a plan to open the building up to eliminate social stigma.
"We were trying to live together with the community," he says.
And it seemed to be having an effect. More and more local residents were visiting the facility to celebrate festivals with the people who live there.
But Tate now has a dilemma. After Tuesday's stabbing, the prefectural authority urged him to tighten security. He used to close the building's gate at 10 p.m., but now tries to make sure it's closed all day.
"It's truly regrettable and a severe situation that we have to limit access to the facility," Tate says.
For Kubo, it's important to let others know that people with disabilities do have families who care about them. One small example of her love is a scarf she gave Jusuke 10 years ago. He's worn it ever since.
She says she wants everyone to know a family bond is not affected even if there are challenges in communicating.
"He is an essential part of our family and brings us all closer together," Kubo says.
Support groups like Kubo's say they're determined to keep promoting the rights of people with disabilities. And call on everyone in Japan to recognize the importance of respecting each and every human being.